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If a = 4b, what percent of 2a is 2b?

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by GMATGuruNY » Mon May 14, 2018 2:42 am
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VJesus12 wrote:If a = 4b, what percent of 2a is 2b?

(A) 10%
(B) 20%
(C) 25%
(D) 26%
(E) 40%
Let b=1, implying that a = 4b = 4*1 = 4.
What percent of 2a is 2b?
2b/2a = b/a = 1/4 = 25%.

The correct answer is C.
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by Brent@GMATPrepNow » Mon May 14, 2018 5:53 am
VJesus12 wrote:If a = 4b, what percent of 2a is 2b?

(A) 10%
(B) 20%
(C) 25%
(D) 26%
(E) 40%

The OA is the option C.

I am confused here. Could anyone help me here? Please. I'd really appreciate it.
I would have used the same approach that Mitch used.
However, here's an algebraic approach:

If a = 4b, then 2a = 8b

What percent of 2a is 2b?
We can rewrite as: 2b/2a = what percent?
Or, we can write: 2b/8b = what percent?
Simplify: 1/4 = what percent?

Since 1/4 = 25%, the correct answer is C

Cheers.
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by Jeff@TargetTestPrep » Tue May 15, 2018 3:37 pm
VJesus12 wrote:If a = 4b, what percent of 2a is 2b?

(A) 10%
(B) 20%
(C) 25%
(D) 26%
(E) 40%
Simplifying, we have:

b/a = 1/4

2b/2a = 1/4 as well, which is 25%.

Answer: C

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