1. ## Divisibility

$18\mid a$ and $a\mid 216 \Rightarrow$ how many a integer?

2. Originally Posted by Sea
$18\mid a$ and $a\mid 216 \Rightarrow$ how many a integer?
All multiples of 18 that divide 216.
Since 216=18*12=18*(1*2*3*4), we can easily list them :
18, 18*2, 18*3, 18*4, 18*6, 18*12

It's in fact 18 multiplied with any number dividing 12.