prep-ps1-154

william0625

154. 16003-!-item-!-187;#058&010661
If n is a positive integer and the product of all the integers from 1 to n, inclusive, is a multiple of 990, what is the least possible value of n ?
(A) 10
(B) 11
(C) 12
(D) 13
(E) 14

答案（b)

990=2*3*3*5*11

求the least possible value of n

为何是11而不是2或是3呢

oooo314585

如果想要是a multiple of 990那就是说

必须是990的factor都得包括在内

如果你让n=2或者3

那11这个factor就不包括了

multiple of 990 = (2*3*3*5*11)*m (m属于正整数)