Pipes and Cisterns Practice Test 1 with solutions

Question : 39 of 40

Marks: +1, -0

Two pipes A and B can fill a cistern in 8 minutes and 12 minutes respectively. Starting with A, if both the pipes are opened alternatively for 1 minute each in what time will they fill the cistern?

9 minutes
10 minutes
$9 1/2$ minutes
$9 3/4$ minutes
$10 1/3$ minutes

Validate

Solution:

Part of cistern filled by A and B in 2 minutes
=

1/8+1/{12}

5/{24}

Part of cistern filled by A and B in 8 minutes
=

5/{24} × 4

{20}/{24}

Part of tank remaining empty =

1 - {20}/{24}

4/{24}

1/6

Part of tank remaining empty after 9 minutes
=

1/6 - 1/8

{4-3}/{24}

1/{24}

Time taken by Pipe B to fill the tank = 12 minutes
Time taken to fill

1/{24}

th part of the tank =

12 × 1/{24}

1/2

minute
So, total time taken to fill the tank =

9 1/2

minutes.

Go to Question:

Prev Question

Next Question