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# By what percent was the price of a smartphone increased? (1) The price

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Math Expert
Joined: 02 Sep 2009
Posts: 58400
By what percent was the price of a smartphone increased? (1) The price  [#permalink]

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09 Oct 2018, 03:19
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5% (low)

Question Stats:

95% (00:34) correct 5% (00:46) wrong based on 47 sessions

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By what percent was the price of a smartphone increased?

(1) The price of the smartphone was increased by $40. (2) The price of the smartphone after the increase was$400.

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Manager
Joined: 23 Jan 2018
Posts: 53
Location: India
Concentration: Operations, Technology
GMAT 1: 650 Q44 V35
GPA: 4
By what percent was the price of a smartphone increased? (1) The price  [#permalink]

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09 Oct 2018, 03:31
1
Bunuel wrote:
By what percent was the price of a smartphone increased?

(1) The price of the smartphone was increased by $40. (2) The price of the smartphone after the increase was$400.

percentage increase = ( Change in price/ old price ) * 100

1- price increased by 40
let the original price be X
new price is X+40
Percentage increase = (40/X)*100 we can't get value out of it.
Statement -1 Not Sufficient

2- new price =400
Old price= X
percentage increase = (400-X/X)*100 we can't get value out of it.
statement-2 not sufficient

Combining Statement 1 and 2:-

New price = 400
Price increased by = 40
Old price = 400-40 = 360
Hence, percentage increase = (40/360)*100 | we got a value

Correct answer should be - C

Give Kudos, if it helped.
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Joined: 19 Oct 2013
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Re: By what percent was the price of a smartphone increased? (1) The price  [#permalink]

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09 Oct 2018, 05:29
Bunuel wrote:
By what percent was the price of a smartphone increased?

(1) The price of the smartphone was increased by $40. (2) The price of the smartphone after the increase was$400.

we want to know the percentage change = $$\frac{New - old}{old} *100$$

1)
Say the old price was a
the new price will be a+40

$$\frac{a+40 - a}{a} = \frac{40}{a}$$ this will depend on the value of a, if it is 80 then 50% increase, if a is 100 then it is 40% increase.

Insufficient

2) we are given that a+increase = 400

$$\frac{400 - a}{a}$$ it does not provide information on the old value.

Combine (1) and (2)

We get $$a + 40 = 400$$

a = 360

$$\frac{400 - 360}{360} = \frac{40}{360} = \frac{1}{9}*100 = 11.11$$

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Re: By what percent was the price of a smartphone increased? (1) The price  [#permalink]

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09 Oct 2018, 08:40
Stmt 1: Gives only change in value. Initial value/final value missing. Hence insufficient.
Cross out A and D

Stmt 2: Gives only final value. Change or initial value, one of the two required. Hence insufficient.
Cross out B

Stmt 1 and Stmt 2: Final value given, change given. So initial value can be calculated. Percentage can be found as 100*(change/initial). Sufficient.

Hence C.

No need to actually calculate values since it is DS!
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Re: By what percent was the price of a smartphone increased? (1) The price   [#permalink] 09 Oct 2018, 08:40
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