Question 10

A student is asked to multiply a number K by 5. But he multiplies K by $$\frac{1}{5}$$ and gets x% error. Next time he multiplies K by $$\frac{1}{25}$$ and gets y% error. Then the percentage increase of y over x is 

Solution

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Originally expected 5K.

but he wrote (1/5)K=0.2K.

first error,x%=(5K-0.2K)/5K=0.96 or 96%.

next time he wrote (1/25)K=0.04K.

second error,y%=(5K0.04K)/5K=0.992 or 99.2%.

so increase of y over x is =

(0.992-0.96)/0.96=0.033333 or 3.33%.

A is correct choice.

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