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nimcet Previous Year Questions (PYQs)

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nimcet PYQ
If $H$ is the harmonic mean between $P$ and $Q$, then $\dfrac{H}{P} + \dfrac{H}{Q}$ is





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nimcet Previous Year PYQ nimcet NIMCET 2012 PYQ

Solution

Harmonic mean of $P$ and $Q$ is $H = \dfrac{2PQ}{P+Q}$
 
 Now, 
$\dfrac{H}{P} + \dfrac{H}{Q} = H\left(\dfrac{1}{P} + \dfrac{1}{Q}\right) = H \cdot \dfrac{P+Q}{PQ}$ 

Substitute 

$H = \dfrac{2PQ}{P+Q}$: 

$\dfrac{H}{P} + \dfrac{H}{Q} = \dfrac{2PQ}{P+Q} \cdot \dfrac{P+Q}{PQ} = 2$
 
So the correct Answer is $2$.

nimcet PYQ
$a,b,c$ are positive and $c>a$ and in H.P. Compute $\log(a+c)+\log(a-2b+c)$.





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nimcet Previous Year PYQ nimcet NIMCET 2011 PYQ

Solution

$a,b,c$ in H.P. ⇒ 

$\dfrac{1}{b} = \dfrac{1}{2}\left(\dfrac{1}{a}+\dfrac{1}{c}\right)$ 

⇒ $2bc = ac + ab$ 

Simplify gives identity: 

$(a+c)(a-2b+c) = (c-b)^2$ 

 Take log: 
$\log(a+c) + \log(a-2b+c) $
$= \log\big((c-b)^2\big)$
$=2\log(c-b)$

nimcet PYQ
Find $k$ in the equation $x^3 - 6x^2 + kx + 64 = 0$ if roots are in geometric progression.





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nimcet Previous Year PYQ nimcet NIMCET 2009 PYQ

Solution

Let roots be $a, ar, ar^2$. 
 Sum of roots: 
$a + ar + ar^2 = 6$ $a(1+r+r^2) = 6$ ...(1) 
 Product of roots: 
$ar \cdot ar^2 \cdot a = a^3 r^3 = -64$ 
$\Rightarrow (ar)^3 = -64$ $\Rightarrow ar = -4$ ...(2) 

 Middle coefficient relation: 
Sum of pairwise products: 
$k = a(ar) + ar(ar^2) + ar^2(a)$ 
$k = a^2 r + a^2 r^3 + a^2 r^2$ 
Factor: $k = a^2 (r + r^2 + r^3)$ 
$k = ar \cdot a(r + r^2 + r^3)$ 
Using (2): $ar = -4$ 
 Also: $r + r^2 + r^3 = r(1 + r + r^2)$ 
 Thus: $k = -4a \cdot r(1 + r + r^2)$ 
 But from (1): $a(1+r+r^2) = 6$ 
 So: $k = -4r \cdot 6 = -24r$ 
 Now solve $ar = -4$ and equation (1). 
Standard GP root problem yields $r = 1$ or $r = -1$. 
Check sign consistency → $r = 1$. 
 So: $k = -24(1)$ 
$k = -24$

nimcet PYQ
The sum of infinite terms of a decreasing GP is equal to the greatest value of the function $f(x)=x^3+3x-9$ in the interval [-2,3] and the difference between the first two terms is $f'(0)$. Then the common ratio of GP is





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nimcet Previous Year PYQ nimcet NIMCET 2019 PYQ

Solution

Given: 

\(f(x)=x^3+3x-9\) on \([-2,3]\). 

Since \(f'(x)=3x^2+3>0\), \(f\) is increasing, so the greatest value is at \(x=3\): 

\(f(3)=27\).

Sum to infinity of decreasing GP: 

\(S=\dfrac{a}{1-r}=27\) with 

Also \(f'(0)=3\Rightarrow\) difference of first two terms: 

\(a-ar=a(1-r)=3\).

From \(a=\;27(1-r)\), 

plug into \(a(1-r)=3\): \(27(1-r)^2=3\Rightarrow(1-r)^2=\dfrac{1}{9}\Rightarrow 1-r=\dfrac{1}{3}\) (take positive)

Common ratio: \(r=1-\dfrac{1}{3}=\boxed{\dfrac{2}{3}}\).


nimcet PYQ
$ \text{The sum of } 11^{2} + 12^{2} + \cdots + 30^{2} \text{ is} $





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nimcet Previous Year PYQ nimcet NIMCET 2011 PYQ

Solution

$ \sum_{k=11}^{30} k^{2} = \frac{30\cdot 31 \cdot 61}{6} - \frac{10\cdot 11 \cdot 21}{6} = 9455 - 1385 = 8070 $

nimcet PYQ
In a G.P. consisting of positive terms, each term equals the sum of the next two terms. Then the common ratio of the G.P. is





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nimcet Previous Year PYQ nimcet NIMCET 2013 PYQ

Solution


nimcet PYQ
If a, b, c are in GP and log a - log 2b, log 2b - log 3c and log 3c - log a are in AP, then a, b, c are the lengths of the sides of a triangle which is





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Solution


nimcet PYQ

Not Available






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Solution



nimcet PYQ
The sum of $n$ terms of an arithmetic series is 216. The value of the first term is $n$ and the value of the $n^{th}$ term is $2n$. The common difference, $d$ is.





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nimcet Previous Year PYQ nimcet NIMCET 2013 PYQ

Solution

Given:
Sum of \(n\) terms = 216
First term \(a = n\)
\(n^{th}\) term \(= 2n\)

Use nth term formula
\[ a_n = a + (n-1)d \] \[ 2n = n + (n-1)d \] \[ n = (n-1)d \quad \cdots (1) \]
Use Sum formula
\[ S_n = \frac{n}{2}(a + a_n) \] \[ 216 = \frac{n}{2}(n + 2n) \] \[ 216 = \frac{n}{2}(3n) \] \[ 216 = \frac{3n^2}{2} \] \[ n^2 = \frac{432}{3} = 144 \] \[ n = 12 \]
Find common difference \(d\)
From equation (1):
\[ n = (n-1)d \] \[ 12 = (12-1)d \] \[ 12 = 11d \] \[ d = \frac{12}{11} \]
Answer: \( d = \dfrac{12}{11} \)


nimcet PYQ
If $a, a, a_2, ., a_{2n-1},b$ are in AP, $a, b_1, b_2,...b_{2n-1}, b $are in GP and $a, c_1, c_2,... c_{2n-1}, b $ are in HP, where a, b are positive, then the equation $a_n x^2-b_n+c_n$ has its roots





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nimcet Previous Year PYQ nimcet NIMCET 2019 PYQ

Solution


nimcet PYQ
If $x=1+\sqrt[{6}]{2}+\sqrt[{6}]{4}+\sqrt[{6}]{8}+\sqrt[{6}]{16}+\sqrt[{6}]{32}$ then ${\Bigg{(}1+\frac{1}{x}\Bigg{)}}^{24}$ =





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nimcet Previous Year PYQ nimcet NIMCET 2024 PYQ

Solution

Given:

\[ x = 1 + 2^{1/6} + 4^{1/6} + 8^{1/6} + 16^{1/6} + 32^{1/6} \]

Step 1: Write in powers of \( a = 2^{1/6} \)

\[ x = 1 + a + a^2 + a^3 + a^4 + a^5 = 1 + \frac{a(a^5 - 1)}{a - 1} \]

Step 2: Use identity \( a^6 = 2 \Rightarrow a^5 = \frac{2}{a} \)

\[ x = 1 + \frac{2 - a}{a - 1} = \frac{1}{a - 1} \Rightarrow 1 + \frac{1}{x} = a \Rightarrow \left(1 + \frac{1}{x} \right)^{24} = a^{24} \]

Step 3: Final calculation

\[ a = 2^{1/6} \Rightarrow a^{24} = (2^{1/6})^{24} = 2^4 = \boxed{16} \]

✅ Final Answer: $\boxed{16}$


nimcet PYQ
The number of solutions of ${5}^{1+|\sin x|+|\sin x{|}^2+\ldots}=25$ for $x\in(-\mathrm{\pi},\mathrm{\pi})$ is





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nimcet Previous Year PYQ nimcet NIMCET 2024 PYQ

Solution

Step 1: Recognize the series

The exponent is an infinite geometric series: $$ 1 + |\sin x| + |\sin x|^2 + |\sin x|^3 + \cdots $$

This is a geometric series with first term \( a = 1 \), common ratio \( r = |\sin x| \in [0,1] \), so: $$ \text{Sum} = \frac{1}{1 - |\sin x|} $$

Step 2: Rewrite the equation

$$ 5^{\frac{1}{1 - |\sin x|}} = 25 = 5^2 $$

Equating exponents: $$ \frac{1}{1 - |\sin x|} = 2 \Rightarrow 1 - |\sin x| = \frac{1}{2} \Rightarrow |\sin x| = \frac{1}{2} $$

Step 3: Solve for \( x \in (-\pi, \pi) \)

We want all \( x \in (-\pi, \pi) \) such that \( |\sin x| = \frac{1}{2} \)

So \( \sin x = \pm \frac{1}{2} \). Within \( (-\pi, \pi) \), the values of \( x \) satisfying this are:

  • $x = \frac{\pi}{6}$
  • $x = \frac{5\pi}{6}$
  • $x = -\frac{\pi}{6}$
  • $x = -\frac{5\pi}{6}$

✅ Final Answer: $\boxed{4}$ solutions


nimcet PYQ
The sum of integers between 200 and 400, that are multiples of 7 is





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nimcet Previous Year PYQ nimcet NIMCET 2013 PYQ

Solution

Step 1: Find the first multiple of 7 after 200
$200 \div 7 = 28.57...$ so first multiple $= 29 \times 7 = 203$

Step 2: Find the last multiple of 7 before 400
$400 \div 7 = 57.14...$ so last multiple $= 57 \times 7 = 399$

Step 3: Identify the AP
First term $a = 203$
Last term $l = 399$
Common difference $d = 7$

Step 4: Find number of terms $n$
$l = a + (n-1)d$
$399 = 203 + (n-1) \times 7$
$399 - 203 = (n-1) \times 7$
$196 = (n-1) \times 7$
$n - 1 = 28$
$n = 29$

Step 5: Find the Sum
$S_n = \dfrac{n}{2}(a + l)$

$S_{29} = \dfrac{29}{2}(203 + 399)$

$S_{29} = \dfrac{29}{2} \times 602$

$S_{29} = 29 \times 301$

$S_{29} = 8729$

Answer: The sum of all multiples of 7 between 200 and 400 is $\boxed{8729}$


nimcet PYQ
Which term of the series $\frac{\sqrt[]{5}}{3},\, \frac{\sqrt[]{5}}{4},\frac{1}{\sqrt[]{5}},\, ...$ is $\frac{\sqrt{5}}{13}$ ?





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nimcet Previous Year PYQ nimcet NIMCET 2022 PYQ

Solution

Step 1: Rewrite all terms with same numerator
$\dfrac{\sqrt{5}}{3},\ \dfrac{\sqrt{5}}{4},\ \dfrac{\sqrt{5}}{5},\ \ldots$

(Since $\dfrac{1}{\sqrt{5}} = \dfrac{\sqrt{5}}{5}$)

Step 2: Identify the AP in denominators
Denominators: $3,\ 4,\ 5,\ \ldots$
First term $a = 3$
Common difference $d = 1$

Step 3: Set up the equation
The $n^{th}$ term of the series $= \dfrac{\sqrt{5}}{a + (n-1)d}$

Given $n^{th}$ term $= \dfrac{\sqrt{5}}{13}$

So denominator of $n^{th}$ term $= 13$

Step 4: Solve for $n$
$a + (n-1)d = 13$
$3 + (n-1) \times 1 = 13$
$n - 1 = 10$
$n = 11$

Answer: $\dfrac{\sqrt{5}}{13}$ is the $\boxed{11^{th}}$ term of the series.


nimcet PYQ
Sum of 20 terms of the series $–1^{2} + 2^{2} –3^{2} + 4^{2} – …$ is





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nimcet Previous Year PYQ nimcet NIMCET 2013 PYQ

Solution

Step 1: Group terms in pairs
$(-1^2 + 2^2) + (-3^2 + 4^2) + (-5^2 + 6^2) + \ldots$

Since 20 terms $\Rightarrow$ there are $\dfrac{20}{2} = 10$ pairs.

Step 2: Simplify each pair
Each pair is of the form $-(2k-1)^2 + (2k)^2$ where $k = 1, 2, 3, \ldots, 10$

$= (2k)^2 - (2k-1)^2$

Using $a^2 - b^2 = (a+b)(a-b)$:

$= (2k + 2k - 1)(2k - 2k + 1)$

$= (4k - 1)(1)$

$= 4k - 1$

Step 3: Sum all 10 pairs
$S = \displaystyle\sum_{k=1}^{10} (4k - 1)$

$= 4\displaystyle\sum_{k=1}^{10} k \ - \ \displaystyle\sum_{k=1}^{10} 1$

$= 4 \times \dfrac{10 \times 11}{2} - 10$

$= 4 \times 55 - 10$

$= 220 - 10$

$= 210$

Answer: Sum of 20 terms $= \boxed{210}$


nimcet PYQ
In a Harmonic Progression, $p^{th}$ term is $q$ and the $q^{th}$ term is $p$. Then $pq^{th}$ term is





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nimcet Previous Year PYQ nimcet NIMCET 2022 PYQ

Solution

Key Concept: If a sequence is in HP, then the reciprocals of its terms are in AP.

Step 1: Convert HP to AP
Let the corresponding AP have first term $a$ and common difference $d$.

$p^{th}$ term of HP $= q$
$\Rightarrow p^{th}$ term of AP $= \dfrac{1}{q}$

$\Rightarrow a + (p-1)d = \dfrac{1}{q} \quad \cdots (1)$

$q^{th}$ term of HP $= p$
$\Rightarrow q^{th}$ term of AP $= \dfrac{1}{p}$

$\Rightarrow a + (q-1)d = \dfrac{1}{p} \quad \cdots (2)$

Step 2: Subtract equation (1) from (2)
$(q - p)d = \dfrac{1}{p} - \dfrac{1}{q}$

$(q - p)d = \dfrac{q - p}{pq}$

$d = \dfrac{1}{pq}$

Step 3: Find $a$ using equation (1)
$a + (p-1) \times \dfrac{1}{pq} = \dfrac{1}{q}$

$a = \dfrac{1}{q} - \dfrac{p-1}{pq}$

$a = \dfrac{p - (p-1)}{pq}$

$a = \dfrac{1}{pq}$

Step 4: Find the $pq^{th}$ term of AP
$T_{pq} = a + (pq - 1)d$

$= \dfrac{1}{pq} + (pq-1) \times \dfrac{1}{pq}$

$= \dfrac{1}{pq} + \dfrac{pq - 1}{pq}$

$= \dfrac{1 + pq - 1}{pq}$

$= \dfrac{pq}{pq} = 1$

Step 5: Convert back to HP
$pq^{th}$ term of HP $= \dfrac{1}{T_{pq}} = \dfrac{1}{1} = 1$

Answer: The $pq^{th}$ term of the HP is $\boxed{1}$


nimcet PYQ
If one AM (Arithmetic mean) 'a' and two GM's (Geometric means) p and q be inserted between any two positive numbers, the value of p^3+q^3 is





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nimcet Previous Year PYQ nimcet NIMCET 2024 PYQ

Solution

Problem:

If one Arithmetic Mean (AM) \( a \) and two Geometric Means \( p \) and \( q \) are inserted between any two positive numbers, find the value of: \[ p^3 + q^3 \]

Given:

  • Let two positive numbers be \( A \) and \( B \).
  • One AM: \( a = \frac{A + B}{2} \)
  • Two GMs inserted: so the four terms in G.P. are: \[ A, \ p = \sqrt[3]{A^2B}, \ q = \sqrt[3]{AB^2}, \ B \]

Now calculate:

\[ pq = \sqrt[3]{A^2B} \cdot \sqrt[3]{AB^2} = \sqrt[3]{A^3B^3} = AB \]
\[ p^3 = A^2B, \quad q^3 = AB^2 \]
\[ p^3 + q^3 = A^2B + AB^2 = AB(A + B) \]

Also,

\[ 2apq = 2 \cdot \frac{A + B}{2} \cdot AB = AB(A + B) \]

✅ Therefore,

\( \boxed{p^3 + q^3 = 2apq} \)


nimcet PYQ
Suppose $a,b,c$ are in A.P. with common difference $d$. Then $e^{1/c},e^{1/b},e^{1/a}$ are





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nimcet Previous Year PYQ nimcet NIMCET 2008 PYQ

Solution

$\frac{1}{a},\frac{1}{b},\frac{1}{c}$ are in H.P. Exponentials of H.P. form G.P. Answer: $\boxed{\text{G.P.}}$

nimcet PYQ
The number of common terms in the two sequences 17, 21, 25, ..........., 817 and 16, 21, 26, ..........., 851 is





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nimcet Previous Year PYQ nimcet NIMCET 2016 PYQ

Solution

Find the number of common terms in:
Series 1: $17, 21, 25, \ldots, 817$
Series 2: $16, 21, 26, \ldots, 851$

Step 1: Identify both APs
Series 1: $a_1 = 17,\ d_1 = 4$
Series 2: $a_2 = 16,\ d_2 = 5$

Step 2: First common term
By observation, $21$ is the first common term (appears in both series).

Step 3: Find common difference of new AP
Common terms will themselves form an AP.

Common difference $= \text{LCM}(d_1, d_2) = \text{LCM}(4, 5) = 20$

So common terms form AP: $21, 41, 61, \ldots$
with $a = 21,\ d = 20$

Step 4: Find the last common term
Last term must be $\leq$ smaller of the two last terms:
$\min(817, 851) = 817$

$T_n = a + (n-1)d \leq 817$
$21 + (n-1) \times 20 \leq 817$
$(n-1) \times 20 \leq 796$
$n - 1 \leq 39.8$
$n \leq 40.8$

So $n = 40$


nimcet PYQ
If $H_1,H_2,\ldots,H_n$ are $n$ harmonic means between $a$ and $b$, $a\ne b$, then the value of $\dfrac{H_1+a}{H_1-a}+\dfrac{H_n+b}{H_n-b}$ is equal to





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nimcet Previous Year PYQ nimcet NIMCET 2008 PYQ

Solution

Step 1: Convert HP to AP
Since $a, H_1, H_2, \ldots, H_n, b$ is in HP,
$\dfrac{1}{a},\ \dfrac{1}{H_1},\ \ldots,\ \dfrac{1}{H_n},\ \dfrac{1}{b}$ is in AP with $n+2$ terms.

Step 2: Find common difference $d$
$d = \dfrac{\dfrac{1}{b}-\dfrac{1}{a}}{n+1} = \dfrac{a-b}{ab(n+1)}$

Step 3: Find $H_1$ and $H_n$
$\dfrac{1}{H_1} = \dfrac{1}{a} + d = \dfrac{a+bn}{ab(n+1)}$ $\Rightarrow H_1 = \dfrac{ab(n+1)}{a+bn}$

$\dfrac{1}{H_n} = \dfrac{1}{b} - d = \dfrac{an+b}{ab(n+1)}$ $\Rightarrow H_n = \dfrac{ab(n+1)}{an+b}$

Step 4: Evaluate $\dfrac{H_1+a}{H_1-a}$ using Componendo-Dividendo
$\dfrac{H_1}{a} = \dfrac{b(n+1)}{a+bn}$

Applying componendo-dividendo:
$\dfrac{H_1+a}{H_1-a} = \dfrac{b(n+1)+(a+bn)}{b(n+1)-(a+bn)} $
$= \dfrac{a+b(2n+1)}{b-a} \quad \cdots(1)$

Step 5: Evaluate $\dfrac{H_n+b}{H_n-b}$ using Componendo-Dividendo
$\dfrac{H_n}{b} = \dfrac{a(n+1)}{an+b}$

Applying componendo-dividendo:
$\dfrac{H_n+b}{H_n-b} = \dfrac{a(n+1)+(an+b)}{a(n+1)-(an+b)} $
$= \dfrac{b+a(2n+1)}{a-b} \quad \cdots(2)$

Step 6: Add (1) and (2)
$\dfrac{H_1+a}{H_1-a}+\dfrac{H_n+b}{H_n-b} $
$= \dfrac{a+b(2n+1)}{b-a} + \dfrac{b+a(2n+1)}{a-b}$

$= \dfrac{a+b(2n+1) - b - a(2n+1)}{b-a}$

$= \dfrac{(a-b) + (2n+1)(b-a)}{b-a}$

$= \dfrac{(b-a)(2n+1)-(b-a)}{b-a}$

$= (2n+1) - 1$

$= 2n$

Answer: $\dfrac{H_1+a}{H_1-a}+\dfrac{H_n+b}{H_n-b} = \boxed{2n}$

nimcet PYQ
Sum to infinity of a geometric is twice the sum of the first two terms. Then what are the possible values of common ratio?





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nimcet Previous Year PYQ nimcet NIMCET 2018 PYQ

Solution

Let first term $= a$ and common ratio $= r$, where $|r| < 1$

Sum to infinity: $S_{\infty} = \dfrac{a}{1-r}$

Sum of first two terms: $S_2 = a + ar = a(1+r)$

Step 2: Set up the equation
Given: $S_{\infty} = 2 \times S_2$

$\dfrac{a}{1-r} = 2 \cdot a(1+r)$

Step 3: Simplify
Dividing both sides by $a$ (since $a \ne 0$):

$\dfrac{1}{1-r} = 2(1+r)$

$1 = 2(1+r)(1-r)$

$1 = 2(1 - r^2)$

$1 = 2 - 2r^2$

$2r^2 = 1$

$r^2 = \dfrac{1}{2}$

$r = \pm\dfrac{1}{\sqrt{2}}$


nimcet PYQ
Suppose that m and n are fixed numbers such that the mth term of an HP is equal to n and the nth term is equal to m, (m ≠ n). Then the (m + n)th term is:





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Solution

Given: The sequence is in H.P. with \(a_m = n\) and \(a_n = m\) \((m \ne n)\).

In an H.P., reciprocals of terms form an A.P. So, \(\tfrac{1}{a_m} = \tfrac{1}{n}\) and \(\tfrac{1}{a_n} = \tfrac{1}{m}\).

This A.P. leads to common difference \(d = \tfrac{1}{mn}\) and first term \(A = \tfrac{1}{mn}\).

Thus, the reciprocal of the \((m+n)\)th term is:

\(b_{m+n} = \tfrac{m+n}{mn}\)

Hence, the \((m+n)\)th term of H.P. is:

\(a_{m+n} = \dfrac{mn}{m+n}\)

Final Answer: \( \dfrac{mn}{m+n} \)

nimcet PYQ
The harmonic mean of two numbers is 4. Their arithmetic mean A and the geometric mean G satisfy the relation 2A+G2 = 27, then the two numbers are





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nimcet Previous Year PYQ nimcet NIMCET 2017 PYQ

Solution

Short Solution:

Let the two numbers be \( a \) and \( b \).

Given: Harmonic mean is 4: $$\frac{2ab}{a + b} = 4 \quad \text{(1)}$$ Arithmetic mean \( A = \frac{a + b}{2} \),
Geometric mean \( G = \sqrt{ab} \)

Given: $$2A + G^2 = 27$$ $$2 \cdot \frac{a + b}{2} + ab = 27 \Rightarrow a + b + ab = 27 \quad \text{(2)}$$ From (1): Multiply both sides by \( a + b \): $$2ab = 4(a + b) \Rightarrow ab = 2(a + b) \quad \text{(3)}$$ Substitute (3) into (2): $$a + b + 2(a + b) = 27 \Rightarrow 3(a + b) = 27 \Rightarrow a + b = 9$$ Then from (3): $$ab = 2 \cdot 9 = 18$$ Now solve: $$x^2 - (a + b)x + ab = 0 \Rightarrow x^2 - 9x + 18 = 0$$ $$\Rightarrow x = 3, 6$$
Final Answer:
$$\boxed{3 \text{ and } 6}$$

nimcet PYQ
If $a, b, c$ are in A.P., $p, q, r$ are in H.P. and $ap, bq, cr$ in G.P.$,$ then $\frac{p}{r} + \frac{r}{p}$ is equal to





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nimcet Previous Year PYQ nimcet NIMCET 2010 PYQ

Solution

$a, b, c$ in A.P. 
⇒ $b = \frac{a+c}{2}$ 

$p, q, r$ in H.P. 
⇒ $\frac{1}{p}, \frac{1}{q}, \frac{1}{r}$ in A.P. 

 Given $ap, bq, cr$ in G.P.

 $\frac{bq}{ap} = \frac{cr}{bq}$ 

 Substitute $b = \frac{a+c}{2}$ and simplify: $\frac{p}{r} + \frac{r}{p} = \frac{a}{c} + \frac{c}{a}$

nimcet PYQ
The number of all even integers between 99 and 999 which are not multiple of 3 and 5 is





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nimcet Previous Year PYQ nimcet NIMCET 2025 PYQ

Solution

Solution:

Even numbers from 100 to 998: count $= \frac{998-100}{2}+1=450$.

Exclude evens divisible by $3$ or $5$ using inclusion–exclusion:

  • Multiples of $6$ in $[100,998]$: $\lfloor 998/6 \rfloor-\lfloor 99/6 \rfloor = 166-16=150$.
  • Multiples of $10$ in $[100,998]$: $\lfloor 998/10 \rfloor-\lfloor 99/10 \rfloor = 99-9=90$.
  • Multiples of $30$ in $[100,998]$: $\lfloor 998/30 \rfloor-\lfloor 99/30 \rfloor = 33-3=30$.

Forbidden $=150+90-30=210$ ⇒ Allowed $=450-210={240}$.


nimcet PYQ
Three positive number whose sum is 21 are in arithmetic progression. If 2, 2, 14 are added to them respectively then resulting numbers are in geometric progression. Then which of the following is not among the three numbers?





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nimcet Previous Year PYQ nimcet NIMCET 2017 PYQ

Solution

Let the three terms in A.P. be a – d, a, a + d.
given that a – d + a + a + d = 21  
a = 7
then the three term in A.P. are 7 – d, 7, 7 + d
According to given condition 9 – d, 9, 21 + d are in G.P.
(9)2 = (9 – d) (21 + d)
81 = 189 + 9d – 21d – d2
81 = 189 – 12d – d2
d2 + 12d – 108 = 0
d(d + 18) – 6 (d + 18) = 0
(d – 6) (d + 18) = 0
We get, d = 6, –18
Putting d = 6 in the term 7 – d, 7, 7 + d we get 1, 7, 13.

nimcet PYQ
If $H_1,H_2,\ldots,H_n$ are n harmonic means between a and b $(b\ne a)$;,then $\frac{{{H}}_n+a}{{{H}}_n-a}+\frac{{{H}}_n+b}{{{H}}_n-b}$





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nimcet Previous Year PYQ nimcet NIMCET 2021 PYQ

Solution

Step 1: Convert HP to AP
Since $a, H_1, H_2, \ldots, H_n, b$ is in HP,
$\dfrac{1}{a},\ \dfrac{1}{H_1},\ \ldots,\ \dfrac{1}{H_n},\ \dfrac{1}{b}$ is in AP with $n+2$ terms.

Step 2: Find common difference $d$
$d = \dfrac{\dfrac{1}{b}-\dfrac{1}{a}}{n+1} = \dfrac{a-b}{ab(n+1)}$

Step 3: Find $H_1$ and $H_n$
$\dfrac{1}{H_1} = \dfrac{1}{a} + d = \dfrac{a+bn}{ab(n+1)}$ $\Rightarrow H_1 = \dfrac{ab(n+1)}{a+bn}$

$\dfrac{1}{H_n} = \dfrac{1}{b} - d = \dfrac{an+b}{ab(n+1)}$ $\Rightarrow H_n = \dfrac{ab(n+1)}{an+b}$

Step 4: Evaluate $\dfrac{H_1+a}{H_1-a}$ using Componendo-Dividendo
$\dfrac{H_1}{a} = \dfrac{b(n+1)}{a+bn}$

Applying componendo-dividendo:
$\dfrac{H_1+a}{H_1-a} = \dfrac{b(n+1)+(a+bn)}{b(n+1)-(a+bn)} $
$= \dfrac{a+b(2n+1)}{b-a} \quad \cdots(1)$

Step 5: Evaluate $\dfrac{H_n+b}{H_n-b}$ using Componendo-Dividendo
$\dfrac{H_n}{b} = \dfrac{a(n+1)}{an+b}$

Applying componendo-dividendo:
$\dfrac{H_n+b}{H_n-b} = \dfrac{a(n+1)+(an+b)}{a(n+1)-(an+b)} $
$= \dfrac{b+a(2n+1)}{a-b} \quad \cdots(2)$

Step 6: Add (1) and (2)
$\dfrac{H_1+a}{H_1-a}+\dfrac{H_n+b}{H_n-b} $
$= \dfrac{a+b(2n+1)}{b-a} + \dfrac{b+a(2n+1)}{a-b}$

$= \dfrac{a+b(2n+1) - b - a(2n+1)}{b-a}$

$= \dfrac{(a-b) + (2n+1)(b-a)}{b-a}$

$= \dfrac{(b-a)(2n+1)-(b-a)}{b-a}$

$= (2n+1) - 1$

$= 2n$

Answer: $\dfrac{H_1+a}{H_1-a}+\dfrac{H_n+b}{H_n-b} = \boxed{2n}$

nimcet PYQ
If $a_1, a_2,...a_n$  are positive real numbers whose product is a fixed number c, then the minimum of $a_1, a_2, ....2a_n$ is





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nimcet Previous Year PYQ nimcet NIMCET 2018 PYQ

Solution

Key Concept: AM-GM Inequality
$\dfrac{a_1 + a_2 + \cdots + a_n}{n} \geq (a_1 \cdot a_2 \cdots a_n)^{1/n}$

Step 1: Rewrite the sum
$a_1 + a_2 + \cdots + a_{n-1} + 2a_n$

This has $n$ terms: $(a_1, a_2, \ldots, a_{n-1}, 2a_n)$

Step 2: Apply AM-GM
$\dfrac{a_1 + a_2 + \cdots + a_{n-1} + 2a_n}{n} \geq (a_1 \cdot a_2 \cdots a_{n-1} \cdot 2a_n)^{1/n}$

$\geq (2 \cdot a_1 a_2 \cdots a_n)^{1/n}$

$\geq (2c)^{1/n}$

Step 3: Find minimum
$a_1 + a_2 + \cdots + 2a_n \geq n(2c)^{1/n}$

Minimum value $= n(2c)^{1/n}$

Equality holds when $a_1 = a_2 = \cdots = a_{n-1} = 2a_n$

Answer: Minimum value $= \boxed{n(2c)^{1/n}}$

nimcet PYQ
The four geometric means between 2 and 64 are 





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nimcet Previous Year PYQ nimcet NIMCET 2021 PYQ

Solution

Step 1: Set up the GP
The sequence is: $2,\ G_1,\ G_2,\ G_3,\ G_4,\ 64$
Total terms $= 6$, so $n = 6$

Step 2: Find common ratio $r$
$a = 2,\ a_6 = 64$

$a_6 = a \cdot r^{n-1}$
$64 = 2 \cdot r^5$
$r^5 = 32$
$r^5 = 2^5$
$r = 2$

Step 3: Find the four geometric means
$G_1 = ar = 2 \times 2 = 4$
$G_2 = ar^2 = 2 \times 4 = 8$
$G_3 = ar^3 = 2 \times 8 = 16$
$G_4 = ar^4 = 2 \times 16 = 32$

Answer: The four geometric means are $\boxed{4, 8, 16, 32}$


nimcet PYQ
Suppose $t_1, t_2, ...t_5$ are in AP such that $\sum ^{18}_{l=0}{{t}}_{3l+1}=1197$ and ${{t}}_7+{{3}}t_{22}=174$. If $\sum ^9_{l=1}{{{t}}_l}^2=947b$, then the value of $b$ is





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nimcet Previous Year PYQ nimcet NIMCET 2025 PYQ

Solution

Let first term $= a$, common difference $= d$, so $t_n = a + (n-1)d$

Step 1: Expand $\displaystyle\sum_{l=0}^{18} t_{3l+1} = 1197$
Terms: $t_1, t_4, t_7, \ldots, t_{55}$ (19 terms, $l = 0$ to $18$)

$t_{3l+1} = a + 3ld$

$\displaystyle\sum_{l=0}^{18}(a + 3ld) $
$= 19a + 3d\cdot\dfrac{18 \times 19}{2} $
$= 19a + 513d = 1197$

$\Rightarrow a + 27d = 63 \quad \cdots(1)$

Step 2: Use $t_7 + 3t_{22} = 174$
$t_7 = a + 6d,\quad t_{22} = a + 21d$

$(a + 6d) + 3(a + 21d) = 174$
$4a + 69d = 174 \quad \cdots(2)$

Step 3: Solve (1) and (2)
From (1): $a = 63 - 27d$

Substitute in (2):
$4(63 - 27d) + 69d = 174$
$252 - 108d + 69d = 174$
$-39d = -78$
$d = 2$

$a = 63 - 54 = 9$

Step 4: Find $\displaystyle\sum_{l=1}^{9} t_l^2$
$t_l = 9 + (l-1) \times 2 = 7 + 2l$

$\displaystyle\sum_{l=1}^{9} t_l^2 = \sum_{l=1}^{9}(7+2l)^2 = \sum_{l=1}^{9}(49 + 28l + 4l^2)$

$= 49(9) + 28\cdot\dfrac{9 \times 10}{2} + 4\cdot\dfrac{9 \times 10 \times 19}{6}$

$= 441 + 1260 + 1140$

$= 2841$

Step 5: Find $b$
$947b = 2841$

$b = \dfrac{2841}{947} = 3$

Answer: $b = \boxed{3}$

nimcet PYQ
If a, b, c are in geometric progression, then $log_{ax}^{a}, log_{bx}^{a}$ and $log_{cx}^{a}$ are in





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nimcet Previous Year PYQ nimcet NIMCET 2015 PYQ

Solution

$ a, b, c $ are in G.P. 

$ \Rightarrow b^2 = ac $ 

Take logs base $a$: 

$ \log_a a = 1,\quad \log_a b,\quad \log_a c $ 

Since $ a, b, c $ are in G.P. 

$ \Rightarrow \log_a a,\ \log_a b,\ \log_a c $ are in A.P. 

Now given: 
$ \log_a(ax) = \log_a a + \log_a x = 1 + \log_a x $

$ \log_a(bx) = \log_a b + \log_a x $
 
$ \log_a(cx) = \log_a c + \log_a x $
 
These are: $ (1 + k),\ (\log_a b + k),\ (\log_a c + k) $ where $k = \log_a x$ 

Adding same constant does not change A.P. nature $\boxed{\text{They are in A.P.}}$

nimcet PYQ
The value of the sum $\frac{1}{2\sqrt{1}+1\sqrt{2}}+\frac{1}{3\sqrt{2}+2\sqrt{3}}+\frac{1}{4\sqrt{3}+3\sqrt{4}}+...+\frac{1}{25\sqrt{24}+24\sqrt{25}}$ is





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nimcet Previous Year PYQ nimcet NIMCET 2015 PYQ

Solution

Step 1: General term
$T_n = \dfrac{1}{(n+1)\sqrt{n}+n\sqrt{n+1}}$

Step 2: Rationalize by multiplying numerator and denominator by $(n+1)\sqrt{n}-n\sqrt{n+1}$
Denominator becomes:
$[(n+1)\sqrt{n}]^2 - [n\sqrt{n+1}]^2$

$ = n(n+1)^2 - n^2(n+1) $
$= n(n+1)(n+1-n)$
$ = n(n+1)$

So:
$T_n = \dfrac{(n+1)\sqrt{n} - n\sqrt{n+1}}{n(n+1)}$

$= \dfrac{\sqrt{n}}{n} - \dfrac{\sqrt{n+1}}{n+1}$

$= \dfrac{1}{\sqrt{n}} - \dfrac{1}{\sqrt{n+1}}$

Step 3: Telescoping sum from $n=1$ to $n=24$
$\displaystyle\sum_{n=1}^{24} T_n = \left(\dfrac{1}{\sqrt{1}} - \dfrac{1}{\sqrt{2}}\right) + \left(\dfrac{1}{\sqrt{2}} - \dfrac{1}{\sqrt{3}}\right) + \cdots + \left(\dfrac{1}{\sqrt{24}} - \dfrac{1}{\sqrt{25}}\right)$

$= \dfrac{1}{\sqrt{1}} - \dfrac{1}{\sqrt{25}}$

$= 1 - \dfrac{1}{5}$

$= \dfrac{4}{5}$

Answer: $\boxed{\dfrac{4}{5}}$

nimcet PYQ
An arithmetic progression has 3 as its first term. Also, the sum of the first 8 terms is twice the sum of the first 5 terms. Then what is the common difference?





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nimcet Previous Year PYQ nimcet NIMCET 2020 PYQ

Solution

Step 1: Write sum formula
$S_n = \dfrac{n}{2}[2a + (n-1)d]$

$S_8 = \dfrac{8}{2}[6 + 7d] $
$= 4(6+7d) $
$= 24 + 28d$

$S_5 = \dfrac{5}{2}[6 + 4d] $
$= \dfrac{5}{2}(6+4d) $
$= 15 + 10d$

Step 2: Apply condition $S_8 = 2S_5$
$24 + 28d = 2(15 + 10d)$
$24 + 28d = 30 + 20d$
$8d = 6$
$d = \dfrac{3}{4}$

Answer: $d = \boxed{\dfrac{3}{4}}$



nimcet PYQ
A group of 630 children is arranged in rows for a group photograph session.
Each row contains three fewer children than the row in front of it.
What number of rows is not possible?






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nimcet Previous Year PYQ nimcet NIMCET 2008 PYQ

Solution

Step 1: Set up AP
Let first row (front) have $a$ children, common difference $d = -3$

For $n$ rows, sum $= 630$:
$S_n = \dfrac{n}{2}[2a + (n-1)(-3)] = 630$

$n[2a - 3(n-1)] = 1260$

$2a = \dfrac{1260}{n} + 3(n-1)$

$a = \dfrac{630}{n} + \dfrac{3(n-1)}{2}$

Step 2: Conditions for valid solution
$a$ must be a positive integer, and last row $= a + (n-1)(-3) > 0$

$\Rightarrow a > 3(n-1)$

$\Rightarrow \dfrac{630}{n} + \dfrac{3(n-1)}{2} > 3(n-1)$

$\Rightarrow \dfrac{630}{n} > \dfrac{3(n-1)}{2}$

$\Rightarrow 1260 > 3n(n-1)$

$\Rightarrow n(n-1) < 420$

$\Rightarrow n \leq 21$ (since $21 \times 20 = 420$, not $< 420$, so $n \leq 20$)

Step 3: Also $a$ must be a positive integer
$a = \dfrac{630}{n} + \dfrac{3(n-1)}{2}$ must be a positive integer.

For $a$ to be integer: $\dfrac{630}{n}$ and $\dfrac{3(n-1)}{2}$ must together give integer.

Check $n = 6$: $a = \dfrac{630}{6} + \dfrac{3(5)}{2} = 105 + 7.5 = 112.5$ — not integer!

Check $n = 7$: $a = \dfrac{630}{7} + \dfrac{3(6)}{2} = 90 + 9 = 99$ ✓
Check $n = 9$: $a = \dfrac{630}{9} + \dfrac{3(8)}{2} = 70 + 12 = 82$ ✓
Check $n = 14$: $a = \dfrac{630}{14} + \dfrac{3(13)}{2} = 45 + 19.5 = 64.5$ — not integer!


nimcet PYQ
The sum of the expression $\dfrac{1}{\sqrt{1}+\sqrt{2}}+\dfrac{1}{\sqrt{2}+\sqrt{3}}+\dfrac{1}{\sqrt{3}+\sqrt{4}}+\cdots+\dfrac{1}{\sqrt{80}+\sqrt{81}}$ is





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nimcet Previous Year PYQ nimcet NIMCET 2016 PYQ

Solution


nimcet PYQ
The sum of infinite terms of decreasing GP is equal to the greatest value of the function $f(x) = x^3 + 3x – 9$ in the interval [–2, 3] and difference between the first two terms is f '(0). Then the common ratio of the GP is





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nimcet Previous Year PYQ nimcet NIMCET 2023 PYQ

Solution

? GP and Function Relation

Given: \( f(x) = x^3 + 3x - 9 \)

The sum of infinite GP = max value of \( f(x) \) on [−2, 3]

The difference between first two terms = \( f'(0) \)


Step 1: \( f(x) \) is increasing ⇒ Max at \( x = 3 \)

\( f(3) = 27 \Rightarrow \frac{a}{1 - r} = 27 \)

Step 2: \( f'(x) = 3x^2 + 3 \Rightarrow f'(0) = 3 \)

⇒ \( a(1 - r) = 3 \)

Step 3: Solve:
\( a = 27(1 - r) \)
\( \Rightarrow 27(1 - r)^2 = 3 \Rightarrow (1 - r)^2 = \frac{1}{9} \Rightarrow r = \frac{2}{3} \)

✅ Final Answer: \( r = \frac{2}{3} \)


nimcet PYQ
If $a_1,a_2,\ldots,a_n$ are in A.P. and $a_1=0$ then the value of $\left(\dfrac{a_3}{a_2}+\dfrac{a_4}{a_3}+\cdots+\dfrac{a_n}{a_{n-1}}\right)-a_2\left(\dfrac{1}{a_2}+\dfrac{1}{a_3}+\cdots+\dfrac{1}{a_{n-2}}\right)$ is equal to





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nimcet Previous Year PYQ nimcet NIMCET 2016 PYQ

Solution


nimcet PYQ
If a, b, c, d are in HP and arithmetic mean of ab, bc, cd is 9 then which of the following number is the value of ad?





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nimcet Previous Year PYQ nimcet NIMCET 2023 PYQ

Solution

$a, b, c, d$ are in H.P. 

$\Rightarrow \frac{1}{a}, \frac{1}{b}, \frac{1}{c}, \frac{1}{d}$ are in A.P.
 
$\Rightarrow \frac{2}{b} = \frac{1}{a} + \frac{1}{c}$ and $\frac{2}{c} = \frac{1}{b} + \frac{1}{d}$


Given A.M. of $ab, bc, cd$ is $9$: 

$\frac{ab + bc + cd}{3} = 9$ 

$\Rightarrow ab + bc + cd = 27$

Now multiply: $\frac{2}{b} = \frac{1}{a} + \frac{1}{c} $

$\Rightarrow 2ac = b(a + c)$

$\frac{2}{c} = \frac{1}{b} + \frac{1}{d} \Rightarrow 2bd = c(b + d)$

Multiply both: $4abcd = bc(a + c)(b + d)$

Cancel $bc$: 

$4ad = (a + c)(b + d)$

Expand RHS: 

$4ad = ab + ad + bc + cd$

$\Rightarrow 3ad = ab + bc + cd$
 
But $ab + bc + cd = 27$: 

$\Rightarrow 3ad = 27$ 

$\Rightarrow ad = 9$

$\boxed{9}$


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