1 and 5.
Because it divides evenly into 100.
100 divides into all the multiples of 100, which are infinite.
3
1, 3, 5, 15.
15, when 15 is divided by 15, it equals 1.
One.
One.
17
The number of zeros is determined by how many times 12 divides into 15!. To determine this, since 12 = 22*3, we will look at how many times 2 and 3 divide into 15!. 2 divides 2,6,10,14 once, 4,12 twice, and 8 three times, so that 2 divides 15! exactly 11 times. 3 divides 3,6,12,15 once and 9 twice, so that 3 divides 15! exactly 6 times. From this, we can see that 12 divides into 15! exactly 5 times, since 125=210*35. In other words, the base-12 representation of 15! ends in 5 zeros.
It is: 1
364
1, 2 and 4.