Question 9
The remainder when 1! + 2! + 3! +∙∙∙+95! is divided by 15 is _____________.
Correct Answer: 3
Solution
5! = 120
From 5! on, every next factorial is a factor of 15.
So, the remainder is 1!+2!+3!+4! = 1+2+6+24 = 33
33%15 = 3
Hence, remainder is 3.
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