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1000DS Price of Magzines sold percent

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1000DS Price of Magzines sold percent

by rookiez » Sun Jul 05, 2009 10:32 am
11. If the price of a magazine is to be doubled, by what percent will the number of magazines sold decrease?
(1) The current price of the magazine is $1.00.
(2) For every $0.25 of increase in price, the number of magazines sold will decrease by 10 percent of the number sold at the current price.

OA is C
IMO B
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Source: — Data Sufficiency |
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by DanaJ » Sun Jul 05, 2009 12:26 pm
1 is insufficient since you don't have any info on the algorithm of sales.

2 provides the following info: for each $0.25 price increase, the decrease will be 10% of the original sales figure. This can be "translated" into the following:

Say x is the original price of the magazine. If the price becomes x + 0.25*n, then the sales will drop by n*10%. To calculate the drop in number of magazines sold, all you have to do is find n.

Since we know that the price doubled, then we can establish that x + 0.25*n = 2x, meaning that 0.25*n = x. As you can see, unless you know x, then there's no way of finding n.

This is why you also need statement 1: with x = 1.00 = 0.25*n, n will be 4 and the decrease in number of magazines sold will be n*10% = 40%.
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