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Study Stuff for MCA Examinations - NIMCET
Study Stuff for MCA Examinations - NIMCET
Previous Year Question (PYQs)
The tens digit of $1! + 2! + 3! + 4! + \dots + 49!$ is —
Solution
From $10!$ onward, every factorial ends with at least two zeros. So, only the sum of first nine factorials affects the tens digit. $1! + 2! + 3! + 4! + 5! + 6! + 7! + 8! + 9! = 1 + 2 + 6 + 24 + 120 + 720 + 5040 + 40320 + 362880 = 409113.$ Tens digit = $\boxed{1}.$Online Test Series, Information About Examination,
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