Problem Solving

candygal79 wrote:What is the sum of different positive Prime Factor of 550 ?

A 10

B 11

C 15

D 16

E 18

550 = (2)(5)(5)(11)
So, the DIFFERENT prime factors are 2, 5 and 11
2 + 5 + 11 = [spoiler]18 = E[/spoiler]

Cheers,
Brent

Hi candygal79,

There's a math rule called 'prime factorization' that you might occasionally use on the GMAT. The idea is that any positive number can be "broken down" into a bunch of prime numbers that are multiplied together (unless the number is already prime).

eg 10 = 2x5

Here, we're asked to prime factor 550; this can be done in a set of steps.

550 = 55x10

55 = 5x11
10 = 2x5

So 550 = 2x5x5x11

GMAT assassins aren't born, they're made,
Rich