Question

To fill a tank, tubes P, Q and R take 10 minutes, 7.5 minutes and 6 minutes respectively. The time in minutes that the tubes together will take to fill the tank is:

• A. 5 mins
• B. 2.5 mins
• C. 7.5 mins
• D. 2 mins

Answer 1

The correct option is B

2.5 mins

(P+Q+R) 1 min work = $\frac{1}{10}+\frac{2}{15}+\frac{1}{6}=\frac{2}{5}$

Total time taken tofill the tank by three tubes together = $\frac{5}{2}$ = 2.5 min