gmatbusters wrote:

A large urn contains 100 balls, of which 36% are red and the rest are blue. How many of the blue balls must be removed so that the percentage of red balls in the urn will be 72% (No red balls are to be removed.)

A) 28

B) 32

C) 36

D) 50

E) 64

This took me ~2 mins to understand the question ..

From given info total balls =100, out of which red 36 and blue 64

We have to find total of balls which would make the count of 36 red balls as 72% of the total which has to be done by removal of blue balls.

So lets find value of total balls at which 36 red balls is 72%

Let x be total balls

36/x= 0.72

solve of x we get 50 , since given that total balls are 100 and we have found that @ 50 , 36 red balls would be 72% so we would have to remove 50 out of 64 available blue balls to make the red balls @ 72%, IMO D..

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