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DS: Averages Question

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DS: Averages Question

by DCJ » Tue Sep 22, 2009 9:39 am
Can someone explain?

Ten different items are for sale in a store, and each is sold at a different price. The average (arithmetic mean) price of these 10 items is $165. If the prices of all the items are changed, will the average price increase?

(1)The five most expensive items each increased in price by 10%
(2) The five least expensive items each decreased in price by 10%

Ans: C
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Source: — Data Sufficiency |
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by praky_rules » Wed Sep 23, 2009 4:47 pm
New Average = Old Average + (10% increase in the top 5 priced items + 10% decrease in the bottom 5 priced items)/10.

10% of the top 5 items will be greater than 10% of the bottom 5.

So New Average will be higher than the old average

C.

Two things worth noting are $ 165 is irrelevant and price cannot be negative!(If the numbers were positive and negative, this conclusion is not possible)
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