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N=1991*1993*1995*1997*1999 What is the sum of the hundreds, tens and units digits of N?

 

Find the smallest positive multiple of 21 that has no digit larger than 1.

 

What is the smallest positive integer n such that the rightmost three digits of n! and (n+1)! are the same?

 Oct 17, 2020
edited by Guest  Oct 17, 2020
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1 - Why don't you just multiply them:1991*1993*1995*1997*1999=3160183 6203377055. Sum=0+5+5=10

 

2 - The smallest multiple of 21 with no digits > 1 =101,010

 

3 - The smallest n =10! =3,628,800  and 10+1 =11! =39,916,800

 

 

 
 Oct 17, 2020

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