Question

To fill a tank, tubes P, Q, and R take 10 minutes, 7.5 minutes and 6 minutes respectively. The time 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

Answer: (B), (C)

The correct options are
B

2.5 mins

C

7.5 mins

P's 1 min work = $\frac{1}{10}$
Q's 1 min work = $\frac{1}{7.5}$=$\frac{2}{15}$
R's 1 min work = $\frac{1}{6}$
(P + Q + R)'s 1 min work = $\frac{1}{10}+\frac{2}{15}+\frac{1}{6}=\frac{12}{30}$

$\therefore$ Total time taken to fill the tank by three tubes together = $\frac{5}{2}$ = 2.5 min = 150 seconds