Expert: Sherry Wallin - 8/23/2010

Question
42 is divisible by which of the following numbers 14,8,5,9

Answer
Eric~


There are a lot of ways to answer this question. Just one of the many ways is to prime factor both 42 and all the numbers that 42 possibly will be divisible by.

42 = 2*3*7
14 = 2*7
8 = 2^3 = 2*2*2
5 = 5
9 = 3^2 = 3*3

The only number that has some of the same factors in it is 14 so that is the only number in the group that 42 is divisible by. Otherwise you would just do the long division and any divisor that resulted in a zero remainder would make 42 divisible by it:

42/14 = 3 remainder 0
42/8 = 5 remainder 2 -> not divisible
42/5 = 8 remainder 2 -> not divisible
42/9 = 4 remainder 6 -> not divisible

Math Prof