Quantitative Aptitude Ques 329

Question: A person ordered 5 pairs of black socks and some pairs of brown socks. The price of a black pair was thrice that of a brown pair. While preparing the bill, the bill clerk interchanged the number of black and brown pairs by mistake which increased the bill by 100%. What was the number of pairs of brown socks in the original order?

Options:

A) 10

B) 15

C) 20

D) 25

Show Answer

Answer:

Correct Answer: D

Solution:

  • Let he bought x pairs of brown socks and price of each brown pair = Rs. y Total cost $ =5\times 3y+xy $ Changed cost $ =5\times y+x\times 3y $ According to the question,

$ \Rightarrow $ $ \frac{5y+3xy-(15y+xy)}{15y+xy}\times 100=100% $

$ \Rightarrow $ $ 5y+3xy=15y+xy+15y+xy $

$ \Rightarrow $ $ 5y+3xy=30y+2xy $

$ \Rightarrow $ $ xy=25,y\Rightarrow x=25 $ Hence, original pair of black socks is 25.

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