Solution

1) 78 paise

Take highest coin:
50 → remaining = 28
28 = 10 + 10 + 2 + 2 + 2 + 2

Coins used:
50, 10, 10, 2, 2, 2, 2
Number of coins = 7

2) 69 paise

50 → remaining = 19
19 = 10 + 5 + 2 + 2

Coins used:
50, 10, 5, 2, 2
Number of coins = 5

3) Rs. 1.01 = 101 paise

50 + 25 = 75 → remaining = 26
26 = 10 + 10 + 2 + 2 + 2

Coins used:
50, 25, 10, 10, 2, 2, 2
Number of coins = 7

Total minimum coins:

78 paise → 7 coins
69 paise → 5 coins
101 paise → 7 coins

Total = 7 + 5 + 7 = 19 coins

Answer: 19 coins