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by shikh » Wed Nov 16, 2011 11:56 pm
A store owner decided to raise the price of a particular item by exactly 10%. Of the following which is NOT the new price?
A.$1.10
B.$8.80
C.$11.00
D.$57.30
E.$78.10
OA: D
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by shankar.ashwin » Thu Nov 17, 2011 12:01 am
When an item of price 'X' is raised by 10%, the new cost is '1.1X'

You are given 1.1X here, so the problem is essentially a divisibility test of 11.

All numbers except for D are divisible by 11 and hence could represent a 10% increase in price.

P.S Divisibility test of 11, difference of (sum of alternate terms should be multiple of 11 (or) 0
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by GMATGuruNY » Thu Nov 17, 2011 2:00 am
shankar.ashwin wrote:When an item of price 'X' is raised by 10%, the new cost is '1.1X'

You are given 1.1X here, so the problem is essentially a divisibility test of 11.

All numbers except for D are divisible by 11 and hence could represent a 10% increase in price.

P.S Divisibility test of 11, difference of (sum of alternate terms should be multiple of 11 (or) 0
Another test for divisibility by 11: when a 3-digit integer is a multiple of 11, the middle digit is the sum of the two outer digits.

For example, 781 (answer choice E) is a multiple of 11 because the middle digit (8) is the sum of the two outer digits (7+1=8).

Only answer choice D doesn't pass this test: in 573, the middle digit (7) is not the sum of the two outer digits (5+3=8).
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by Anurag@Gurome » Thu Nov 17, 2011 4:25 am
shikh wrote:A store owner decided to raise the price of a particular item by exactly 10%. Of the following which is NOT the new price?
A.$1.10
B.$8.80
C.$11.00
D.$57.30
E.$78.10
OA: D
What if the original price is (10/11)* 57.3?
Then the new price can be 57.3.
It is better to mention that the original price is an integer.
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by user123321 » Thu Nov 17, 2011 4:55 am
shikh wrote:A store owner decided to raise the price of a particular item by exactly 10%. Of the following which is NOT the new price?
A.$1.10
B.$8.80
C.$11.00
D.$57.30
E.$78.10
OA: D
IMO this question is not well formed. It should have mentioned initial amount was an integer.
Then only D is possible.

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