Average Ques 17
Question-
Three numbers A, B and C are in the ratio 1: 2: 3. Their average is 600. If A is increased by 10% and B is decreased by 20%, then to get the average increased by 5%. C will be increased by [NICL (AO) 2014]
(1) 90%
(2) 10%
(3) 15%
(4) 18%
(5) 20%
Show Answer
Correct Answer: (5)
Solution: (5)
Let A = x, B = 2x and C = 3x
Then, $ \frac{x+2x+3x}{3}=600 $
$ \Rightarrow $ $ \frac{6x}{3}=600 $
$ \frac{x}{3}=100 $
$ \Rightarrow $ $ x=300 $
$ \therefore $ Numbers are 300, 600 and 900.
New average = 105% of $ 600=\frac{600\times 105}{100}=630 $ Now, let
$ \Rightarrow $ $ 300\times \frac{110}{100}+600\times \frac{80}{100}+y=1890 $
$ \Rightarrow $ $ 330+480+y=1890 $
$ \Rightarrow $ $ 810+y=1890 $
$ \Rightarrow $ $ y=1890-810=1080 $
$ \therefore $ Increase in $ C=1080\%-900\%=180\% $
% increase in $ C=\frac{180}{900}\times 100=20\% $
BETA
