Question

$A$ can do a work in $15$ days and $B$ can do the same work in $20$ days, if $A$ and $B$ has done work for $4$ days together, the fraction of work left?

• A. $\frac{2}{15}$
• B. $\frac{7}{13}$
• C. $\frac{8}{15}$
• D. $\frac{1}{5}$
• E. $\frac{16}{15}$

Answer 1

Answer: (C)

Work done by $A$ per day $=\frac{W}{15}$

Let Work done by $B$ per day $=\frac{W}{20}$

Now, using the Given Information

$\Rightarrow (\frac{W}{15}+\frac{W}{20})\ast 4=\frac{28W}{60}$

Now Work left

$\Rightarrow W-\frac{28}{60}W=\frac{32}{60}W=\frac{8}{15}W$

Therefore Answer is $\left(A\right)$