Question

If P, Q and R can do a work in 30, 90 and 45 days respectively. In how many days can P complete the work if Q and R help P every third day?

• A. 20
• B. 15
• C. 23
• D. 24

Answer 1

The correct option is C

23

Work done by P in one day = $\frac{1}{30}$

Work done by Q in one day = $\frac{1}{90}$

Work done by R in one day = $\frac{1}{45}$

Work done in 3 days = $\frac{1}{90}+\frac{1}{45}+\frac{3}{30}=\frac{2}{15}$

In 21 days, $\frac{14}{15}$ of the work will be completed.

Remaining $\frac{1}{15}$ work will be completed by P in 2 days.

Total work will be completed in 23 days.