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By approximately what percent is x greater

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by jbryant62 » Mon Oct 02, 2017 12:46 pm
Vincen wrote:By approximately what percent is x greater than 4/5 if (4/5)(x) = 1?

A. 73%
B. 56%
C. 41%
D. 37%
E. 29%

B is the OA.

How can I do this PS question? Should I substitute each percentage in x?

In order for the equation to equal 1, X has to be the reciprocal of 4/5. So X is 5/4. Fractions are hidden division problems. therefore 4/5 =.8 and 5/4 =1.25. so percent change is (new value-original)/ original. (1.25-.8)/.8-=.5625 or approx. 56%. Or you could have just divided 1.25/.8= 1.5625 therefore it is 56% greater
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by ceilidh.erickson » Mon Oct 02, 2017 12:49 pm
If (4/5)x = 1, then x = 5/4

Target question: by what percent is 5/4 greater than 4/5?

Since these fractions easily convert to decimals, that is the easiest way to calculate the difference: By what percent is 1.25 greater than 0.8?

Percent change = (difference)/(original)
Difference = 1.25 - 0.8 = 0.45
(0.45)/(0.8) = 45/80 = 9/16
--> this is slightly more than half. Look at the answer choices. Since only 56 is slightly more than half, we can pick it without doing any further calculation.

The answer is B.
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by ceilidh.erickson » Mon Oct 02, 2017 12:52 pm
jbryant62 wrote: In order for the equation to equal 1, X has to be the reciprocal of 4/5. So X is 5/4. Fractions are hidden division problems. therefore 4/5 =.8 and 5/4 =1.25. so percent change is (new value-original)/ original. (1.25-.8)/.8-=.5625 or approx. 56%. Or you could have just divided 1.25/.8= 1.5625 therefore it is 56% greater
Since you won't have a calculator on the Quant section of the GMAT, it's not advisable to hand-calculate division such as 1.25/0.8. That would eat up a lot of valuable time. First, estimate. Then, do calculations only if there are answer choices that are too close together; this was not the case here.
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by Brent@GMATPrepNow » Mon Oct 02, 2017 1:54 pm
Once we know that we must determine the percent change from 0.8 to 1.25, might also recognize that 0.4 is 50% of 0.8
So, 1.2 is 50% greater than 0.8 (aside: 0.8 + 0.4 = 1.2)
So, 1.25 must be a LITTLE BIT MORE than 50% greater than 0.8
Check the answer choices....only answer choice B (56%) is a bit more than 50%

Cheers,
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by EconomistGMATTutor » Sat Oct 07, 2017 3:18 pm
Vincen wrote:By approximately what percent is x greater than 4/5 if (4/5)(x) = 1?

A. 73%
B. 56%
C. 41%
D. 37%
E. 29%

B is the OA.

How can I do this PS question? Should I substitute each percentage in x?
Hi Vicen,
Let's take a look at your question.

We can find value of x using the equation:
(4/5)(x) = 1
x = 5/4
x = 1.25

The question states,
"By approximately what percent is x greater than 4/5"
Since x = 1.25 and 4/5 = 0.8
Therefore, we need to find,
By approximately what percent is 1.25 greater than 0.8
It means we need to find the percent change.
Original value = 0.8
New Value = 1.25

Percent Change = [(New Value - Original Value) / Original Value ] * 100%

Percent Change = [(1.25 - 0.8)/0.8] * 100%
Percent Change = [0.45/0.8] * 100%
Percent Change = 0.5625 * 100%
Percent Change = 56.25%
Which is approximately equal to 56%.

Therefore, Option B is correct.

I am available if you'd like any followup.
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Re: By approximately what percent is x greater

by Scott@TargetTestPrep » Fri Jan 24, 2020 9:38 am
Vincen wrote: ↑
Mon Oct 02, 2017 10:08 am
 By approximately what percent is x greater than 4/5 if (4/5)(x) = 1?

A. 73%
B. 56%
C. 41%
D. 37%
E. 29%

B is the OA.

How can I do this PS question? Should I substitute each percentage in x?
Solving for x, we have:

x = 5/4

Thus:

(5/4 - 4/5) / 4/5 x 100 = (1.25 - 0.8)/0.8 x 100 ≈ 0.56 = 56%

Answer: B

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