A large tanker can be filled by two pipes A and B in 60 minutes and 40

1.	A large tanker can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it for the other half? (a) 15 minutes (b) 20 minutes (c) 27.5 minutes (d) 30 minutes
Answer» (d) 30 minutes Let the total time taken to fill the tank be x minutes.Then, work by B in half hour + work done by (A + B) in half hour = 1 \(\big(\frac{1}{40}\times\frac{X}{2}\big)\) + \(\big(\frac{1}{60}+\frac{1}{40}\big)\) x \(\frac{X}{2}\) = 1 \(\Rightarrow\) \(\frac{X}{80}\) + \(\frac{X}{48}\) = 1 \(\Rightarrow\) \(\frac{3X+5X}{240}\) = 1 \(\Rightarrow\) 8x = 240 \(\Rightarrow\) x = 30 min.

A large tanker can be filled by two pipes A and B in 60 minutes and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it for the other half? (a) 15 minutes (b) 20 minutes (c) 27.5 minutes (d) 30 minutes

Answer»

(d) 30 minutes

Let the total time taken to fill the tank be x minutes.Then,

work by B in half hour + work done by (A + B) in half hour = 1

\(\big(\frac{1}{40}\times\frac{X}{2}\big)\) + \(\big(\frac{1}{60}+\frac{1}{40}\big)\) x \(\frac{X}{2}\) = 1

\(\Rightarrow\) \(\frac{X}{80}\) + \(\frac{X}{48}\) = 1 \(\Rightarrow\) \(\frac{3X+5X}{240}\) = 1

\(\Rightarrow\) 8x = 240 \(\Rightarrow\) x = 30 min.