Problem Solving

BTGmoderatorDC wrote:By what percent is 25 greater than 15?

(A) 10%
(B) 25%
(C) 33 1/3%
(D) 60%
(E) 66 2/3%

OA E

Source: Manhattan Prep

25 is greater than 15 by 10 (= 25 - 15). Thus, 25 is greater than 15 by (10/15)*100% = 66 2/3%.

The correct answer: E

Hope this helps!

-Jay
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BTGmoderatorDC wrote:By what percent is 25 greater than 15?

(A) 10%
(B) 25%
(C) 33 1/3%
(D) 60%
(E) 66 2/3%

An alternative approach is to test the answer choices

First, however, we can eliminate some answer choices by first testing an easy value: 50%

Is 25 50% greater than 15?
Well, 50% of 15 = 7.5
So, 50% greater than 15 = 15 + 7.5 = 22.5
22.5 is too small (we need to get 25), so we need a percentage that's greater than 50%
So, we can ELIMINATE A, B and C

Now we'll test answer choice D: 60%
Is 25 60% greater than 15?
60% of 15 = 9
So, 60% greater than 15 = 15 + 9 = 24 (no good - we need 25)
We can ELIMINATE D

By the process of elimination, the correct answer is E

Cheers,
Brent

BTGmoderatorDC wrote:By what percent is 25 greater than 15?

(A) 10%
(B) 25%
(C) 33 1/3%
(D) 60%
(E) 66 2/3%

We can create the following expression:

(25 - 15)/15 x 100 = 10/15 x 100 = 2/3 x 100 = 66 â…”%

Alternate Solution:

We see that 25 is 10 more than 15. Thus, 25 is 10/15 greater than 15. We see that 10/15 = 2/3 ≈ 0.67, or 67%

Answer: E