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 n! the product of the first n integers.
23! = 2585201ab38884976640000.
Without performing multiplications, find the digits denoted here by a and b.
Link to comment
Share on other sites
1 answer to this question
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.