Quantitative Aptitude Ques 1300
Question: Working together A and B can complete a piece of work in 5 days. If A had worked twice as fast the work would have been completed in 4 days. In how many days can A alone complete the work?
Options:
A) $ 20days $
B) $ 6\frac{2}{3}days $
C) $ 18days $
D) $ 6\frac{1}{4}days $
Show Answer
Answer:
Correct Answer: A
Solution:
- Let A do the work in a days.
$ \therefore $ A’s 1 day’s work $ =\frac{1}{a} $ Let B do the work in b days,
$ \therefore $ B’s 1 day’s works $ =\frac{1}{b} $ According to the question, $ \frac{1}{a}+\frac{1}{b}+\frac{1}{5} $ (i) $ \frac{2}{a}+\frac{1}{b}=\frac{1}{4} $ (ii) On solving Eqs. (i) and (ii)i we get
$ \Rightarrow $ $ \frac{1}{a}-\frac{2}{a}=\frac{1}{5}-\frac{1}{4} $
$ \Rightarrow $ $ \frac{1-2}{a}=\frac{4-5}{20} $
$ \Rightarrow $ $ -\frac{1}{a}=-\frac{1}{20} $
$ \Rightarrow $ $ \frac{1}{a}=\frac{1}{20} $
$ \Rightarrow $ $ a=20days $
BETA
