primes

[resilient]

6. What is the largest prime factor of (2^3*3^3*5)+(2^2*3^2*5^2)?
(A) 5
(B) 7
(C) 11
(D) 13
(E) 17

[resilient]

qa is 11

[II]

This is a good question. Where did you get it from ?
I too would be interested in finding out the best way to solve this. Looking forward to see what response some of the moderators/GMAT instructors will give to this post.

[codesnooker]

Too easy question. Remember in such question, try to simplify the equation first.

Let me write the equation and then we will simplify it:-

{(2^3) X (3^3) X (5)} + {(2^2) X (3^2) X (5^2)}

Take out the common factors from the above equation i.e. 2^2, 3^2 and 5

So it will become,

(2^2) X (3^2) X (5) X { (2 X 3 X 1) + (1 X 1 X 5) }

(2^2) X (3^2) X (5) X ( 6 + 5 )

(2^2) X (3^2) X (5) X (11)

So you can check 11 is highest prime factor among 2, 3, 5 and 11.

[resilient]

the source was scoretop and these questions are generally harder. SO basically what I am learning is that we need to simplify first ( key to many questions) then extract the common terms and the answer will be in the addition of the EXTRA terms. correct?!

[codesnooker]

Yup