perplexus.info :: Just Math : Division by e

Division by e (Posted on 2020-03-25)

Let [x] denote the closest integer to x.

Find the last 5 digits of [100000!/e]

No Solution Yet Submitted by Danish Ahmed Khan

Rating: 5.0000 (2 votes)

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Solution with explanation

| Comment 8 of 10 |

100000!/e =100000! (1/1! - 1/2! + .. + 1/100000!) + fractional part

throwing away the fractional part and reversing the order:

100000!/e = 1 - 100000 + (100000)(99999) - bigger stuff

so, 100000!/e ends in 00001

Posted by FrankM on 2020-04-09 11:32:01

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