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Over a three-week period, the price of an ounce of gold

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by swerve » Tue Apr 10, 2018 8:37 am
Over a three-week period, the price of an ounce of gold increased by 25% in the first week, decreased by 20% in the following week, and increased by 5% in the third week. If the price of gold was G dollars per ounce at the beginning of the three weeks, what was the price, in terms of G, at the end of the three weeks?

A. 0.95G
B. G
C. 1.05G
D. 1.1G
E. 1.15G

The OA is C.

Please, can anyone explain this PS question for me? I tried to solve it but I can't get the correct answer. I need your help. Thanks.
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Source: — Problem Solving |

gold price

by GMATGuruNY » Tue Apr 10, 2018 9:01 am
swerve wrote:Over a three-week period, the price of an ounce of gold increased by 25% in the first week, decreased by 20% in the following week, and increased by 5% in the third week. If the price of gold was G dollars per ounce at the beginning of the three weeks, what was the price, in terms of G, at the end of the three weeks?

A. 0.95G
B. G
C. 1.05G
D. 1.1G
E. 1.15G
Let G = 100.
After a 25% increase, the price = 100 + (25/100)(100) = 100 + 25 = 125.
After a 20% decrease, the price = 125 - (20/100)(125) = 125 - 25 = 100.
After a 5% increase, the price = 100 + (5/100)(100) = 100 + 5 = 105.

The question stem asks for the final price: 105.
Now plug G=100 into the answer choices to see which yields a final price of $105.
Only C works:
(1.05)G = (1.05)(100) = 105.

The correct answer is C.
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by Scott@TargetTestPrep » Mon Apr 16, 2018 3:42 pm
swerve wrote:Over a three-week period, the price of an ounce of gold increased by 25% in the first week, decreased by 20% in the following week, and increased by 5% in the third week. If the price of gold was G dollars per ounce at the beginning of the three weeks, what was the price, in terms of G, at the end of the three weeks?

A. 0.95G
B. G
C. 1.05G
D. 1.1G
E. 1.15G
The price of gold at the end of the 3 weeks was:

G x 1.25 x 0.8 x 1.05 = 1.05G = 1.05G

Answer: C

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