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# During a two-week period, the price of an ounce of silver increased by

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During a two-week period, the price of an ounce of silver increased by  [#permalink]

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10 Jan 2014, 07:09
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During a two-week period, the price of an ounce of silver increased by 25 percent by the end of the first week and then decreased by 20 percent of this new price by the end of the second week. If the price of silver was x dollars per ounce at the beginning of the two-week period, what was the price, in dollars per ounce, by the end of the period?

(A) 0.8x
(B) 0.95x
(C) x
(D) 1.05x
(E) 1.25x

Problem Solving
Question: 34
Category: Arithmetic Percents
Page: 66
Difficulty: 600

The Official Guide For GMAT® Quantitative Review, 2ND Edition

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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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10 Jan 2014, 07:09
SOLUTION

During a two-week period, the price of an ounce of silver increased by 25 percent by the end of the first week and then decreased by 20 percent of this new price by the end of the second week. If the price of silver was x dollars per ounce at the beginning of the two-week period, what was the price, in dollars per ounce, by the end of the period?

(A) 0.8x
(B) 0.95x
(C) x
(D) 1.05x
(E) 1.25x

The price by the end of the period = (x*1.25)*0.8 = x.

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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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10 Jan 2014, 11:07
1
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

During a two-week period, the price of an ounce of silver increased by 25 percent by the end of the first week and then decreased by 20 percent of this new price by the end of the second week. If the price of silver was x dollars per ounce at the beginning of the two-week period, what was the price, in dollars per ounce, by the end of the period?

(A) 0.8x
(B) 0.95x
(C) x
(D) 1.05x
(E) 1.25x

After 25% increase , the value is 1.25 x
after 20% decrease, the value is 1.25 * 0.8 * x = x - option C)
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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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11 Jan 2014, 06:58
SOLUTION

During a two-week period, the price of an ounce of silver increased by 25 percent by the end of the first week and then decreased by 20 percent of this new price by the end of the second week. If the price of silver was x dollars per ounce at the beginning of the two-week period, what was the price, in dollars per ounce, by the end of the period?

(A) 0.8x
(B) 0.95x
(C) x
(D) 1.05x
(E) 1.25x

The price by the end of the period = (x*1.25)*0.8 = x.

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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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07 Aug 2014, 02:47
2
Initial Price = x

25% increase$$= \frac{125x}{100}$$

20% decrease$$= \frac{125x}{100} * \frac{80}{100} = x$$

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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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22 Dec 2016, 20:10
1 Week : (1.25)x
2nd Week : (0.80)(1.25)x
x
C
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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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22 Feb 2017, 03:55
Alternate approach when two successive rate changes are given:
final change is =25+(-20)+ (25)(-20)/100 =0

Hence, no change in price after two week.
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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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02 Oct 2018, 21:28
Hi All,

We're told that during a two-week period, the price of an ounce of silver INCREASED by 25 percent by the end of the first week and then DECREASED by 20 percent of this new price by the end of the second week. We're asked, if the price of silver was X dollars per ounce at the beginning of the two-week period, then what was the price, in dollars per ounce, by the end of the period. This question can be approached in a number of different ways; you might find it easiest to convert the percents to fractions and simplify the calculation all at once.

Starting value of an ounce of silver = X
After the 25% increase in price --> (5/4)(X)

The 20% decrease in price means that the value of the silver was 80% of the prior price...
After the 20% decrease of the new price --> (4/5)(5/4)(X)

The product of (4/5) and (5/4) is 20/20 = 1, so we're left with (1)(X) as the price at the end of the 2-week period.

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Re: During a two-week period, the price of an ounce of silver increased by  [#permalink]

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03 Oct 2018, 17:57
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

During a two-week period, the price of an ounce of silver increased by 25 percent by the end of the first week and then decreased by 20 percent of this new price by the end of the second week. If the price of silver was x dollars per ounce at the beginning of the two-week period, what was the price, in dollars per ounce, by the end of the period?

(A) 0.8x
(B) 0.95x
(C) x
(D) 1.05x
(E) 1.25x

By the end of the 2-week period, the price was:

x * 1.25 * 0.8 = x

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Re: During a two-week period, the price of an ounce of silver increased by   [#permalink] 03 Oct 2018, 17:57
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