A man can do a piece of work in 5 days, but with the help of his son, he can doit in 3 days. In what time can the son do it alone?
A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?
A7 days
B8 days
C7.5 days
D6.5 days
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Correct Answer is : 7.5 days
Explanation:
In this type of question, where we have one person work and together work done. Then we can easily get the other person work just by subtracting them. As,
Son's one day work
\(\begin{aligned} \left(\frac{1}{3}-\frac{1}{5} \right) \\ =\left(\frac{5-3}{15} \right) \\ = \frac{2}{15} \end{aligned}\)
So son will do whole work in \(\frac{15}{2}\) days
which is =\(\begin{aligned} 7\frac{1}{2}days \end{aligned}\)
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