SATHEE: Quantitative Aptitude Ques 815

Quantitative Aptitude Ques 815

Question: A and B together can do a work in 12 days. B and C together do it in 15 days. If As efficiency is twice that of C, then the number of days required for B alone to finish the work, is

Options:

A) 60

B) 20

C) 30

D) 15

Show Answer

Answer:

Correct Answer: B

Solution:

Let A can do the work in x days, then C can do the work in 2x days. Let B can do that work in y days.

$ \therefore $ $ \frac{1}{x}+\frac{1}{y}=\frac{1}{12} $

$ \Rightarrow $ $ \frac{1}{y}=\frac{1}{12}-\frac{1}{x} $ and $ \frac{1}{2x}+\frac{1}{y}=\frac{1}{15} $

$ \Rightarrow $ $ \frac{1}{y}=\frac{1}{15}-\frac{1}{2x} $ Solving, $ \frac{1}{12}-\frac{1}{x}=\frac{1}{15}-\frac{1}{2x} $

$ \Rightarrow $ $ \frac{1}{x}-\frac{1}{2x}=\frac{1}{12}-\frac{1}{15} $

$ \Rightarrow $ $ \frac{1}{2x}=\frac{5-4}{60} $
$ \Rightarrow $ $ x=30 $

$ \Rightarrow $ $ \frac{1}{y}=\frac{1}{12}-\frac{1}{x}=\frac{1}{12}-\frac{1}{30} $ $ =\frac{5-2}{60}=\frac{3}{60}=\frac{1}{20} $

$ \therefore $ $ y=20 $

Quantitative Aptitude Ques 814

Quantitative Aptitude Ques 816

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