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# GRE Math Challenge #91- a>0

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GRE Math Challenge #91- a>0 [#permalink]  09 May 2015, 11:09
Expert's post
00:00

Question Stats:

91% (00:26) correct 8% (01:04) wrong based on 23 sessions
a>0

Quantity A: $$(4\sqrt{(5a)})^2$$
Quantity B: 40a

• Quantity A is greater.
• Quantity B is greater.
• Both Quantities are Equal
• Cannot be determined
[Reveal] Spoiler: OA

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Sandy
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Re: GRE Math Challenge #91 [#permalink]  18 May 2015, 11:18
Expert's post
sandy wrote:
a > 0
Quantity A: $$(4\sqrt{(5a)})^2$$
Quantity B: 40a

Quantity A:
[4√(5a)]² = [4√(5a)][4√(5a)]
= (16)(5a)
= 80a

So, we have:
Quantity A: 80a
Quantity B: 40a

Subtract 40a from both quantities to get:
Quantity A: 40a
Quantity B: 0

Divide both quantities by 40 to get:
Quantity A: a
Quantity B: 0

The given information tells us that a > 0, so the correct answer is
[Reveal] Spoiler:
A

Cheers,
Brent
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Brent Hanneson – Creator of greenlighttestprep.com

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Re: GRE Math Challenge #91- a>0 [#permalink]  02 Oct 2017, 01:56
80a 40a
2 1 on dividing
Re: GRE Math Challenge #91- a>0   [#permalink] 02 Oct 2017, 01:56
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