perplexus.info :: Just Math : Factorial Difference Digits

Factorial Difference Digits (Posted on 2014-01-12)

Determine the last two non-zero digits of 36! - 24!

Extra Challenge: Solving this puzzle without a computer program.

See The Solution Submitted by K Sengupta

Rating: 5.0000 (2 votes)

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re: How it could be done with a calculator (spoiler)

| Comment 5 of 6 |

I have got the same 2 last digits by EXCEL column , starting with

a column of 23 numbers 2,3,...24 with 16 replaced by 1 and 5,10,15,20 by 1,2,3,4.

Going down with p(n)=MOD(n*p(n-1),100) resulted with 36.

Answer: the last two digits are 6 and 4.

Posted by Ady TZIDON on 2014-01-13 01:23:57

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