Question

$A$ and $B$ can together finish a work $30$ days. They worked together for $20$ days and then $B$ left. After another $20$ days, $A$ finished the remaining work. In how many days $A$ alone can finish the work?

• A. $40$
• B. $50$
• C. $54$
• D. $60$

Answer 1

The correct option is D $60$

$(A+B)$'s $20$ day's work $=(\frac{1}{30}\times 20)=\frac{2}{3}$.
Remaining work $=(1-\frac{2}{3})=\frac{1}{3}$.
Now, $\frac{1}{3}$ work done by $A$ in $20$ days.
Therefore, the whole work will be done by $A$ in $(20\times 3)=60$ days.