bonanova Posted May 1, 2014 Report Share Posted May 1, 2014 We denote by factorial n! the product of the first n integers. 23! = 2585201ab38884976640000. Without performing multiplications, find the digits denoted here by a and b. Quote Link to comment Share on other sites More sharing options...

0 Rainman Posted May 1, 2014 Report Share Posted May 1, 2014 Sum of all digits = 86+a+b. 9|86+a+b, so a+b equals 4 or 13. Sum of odd position digits - sum of even position digits = 10+b-a. 11|10+b-a, so b-a = 1. Hence b = 7 and a = 6. Quote Link to comment Share on other sites More sharing options...

## Question

## bonanova

We denote by factorial

! the product of the firstnintegers.n23! = 2585201

38884976640000.abWithout performing multiplications, find the digits denoted here by

anda.b## Link to comment

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