Question

$A$ can do a work in $15$ days and B in $20$ days. If they together work on it for $4$ days, what fraction of the work will be left ?

• A. $\frac{1}{13}$
• B. $\frac{6}{11}$
• C. $\frac{9}{17}$
• D. $\frac{8}{15}$

Answer 1

Answer: (D)

$\frac{8}{15}$

Amount of work A can do in 1 day$=\frac{1}{15}$

Amount of work B can do in 1 day $=\frac{1}{20}$

Amount of work done by A and B in 1 day$=\frac{1}{15}+\frac{1}{20}=\frac{7}{60}$

Amount of work A and B can together do in 4 days $=4\times \frac{7}{60}=\frac{7}{15}$

Fraction of work left$=1-\frac{7}{15}=\frac{8}{15}$