Pipe A can fill a tank in 80 min and pipe B can fill the tank in 40 min. If A and B are opened together, then in how many minutes will the tank be filled?

Correct option is B

Given:

Pipe A can fill the tank in 80 minutes

Pipe B can fill the tank in 40 minutes

Required: Time taken for both pipes A and B to fill the tank when opened together

Solution:
The rate of work for a pipe is the reciprocal of the time taken to fill the tank.

Rate of A =$$\frac{1}{80}$$​

Rate of B =$$\frac{1}{40}$$​

When both pipes are opened together, their combined rate is:

Combined Rate $$= \frac{1}{80} + \frac{1}{40} = \frac{1}{80} + \frac{2}{80} = \frac{3}{80}$$​

Time taken =$$\frac{1}{\text{Combined Rate}} = \frac{1}{\frac{3}{80}} = 26\frac{2}{3}$$ minutes

Alternate Method:

Time taken = $$\frac{80} 3 = 26\frac{2}{3}$$ minutes