6. Kai has begun to list, in ascending order, the positive integers which are not factors of 240 . What is the sixth number on Kai's list?
A 11
B 13
C 14
D 15
E 17
6. E In ascending order, the first factors of 240 are $1,2,3,4,5,6,8,10,12,15,16,20$. So the first numbers on Kai's list are 7, 9, 11, 13, 14, 17, 18, 19 . Hence the sixth number on the list is 17 .