Discussion

Explanation:

Let the total work to be done = 12 units.

∴ Efficiency of Pipe A = 12/3 = 4 units/hour.
∴ Efficiency of Pipe B = 12/4 = 3 units/hour.
∴ Efficiency of Pipe c = 12/6 = -2 units/hour. (-ve indicates that it is an emptying pipe)

Between 1 p.m. till 3 p.m., 

For the first 1 hour pipe C would not do any work as the tank is empty initially.

Work done by pipe C from 2 – 3 p.m. = 1 × -2 = -2 units.
Work done by pipe B from 2 – 3 p.m. = 1 × 3 = 3 units.

Total work done till 3 p.m. = 3 – 2 =  1 unit.

Work left = 12 – 1 = 11 units.

Now all three of them work and their combined efficiency = 4 + 3 – 2 = 5 units/hour.

∴ Time taken after 3 p.m. = 11/5 = 2.2 hours i.e., 2 hours 12 mins.

Hence, the tank gets filled 11/5 hours after 3 pm i.e. at 5:12 p.m.

Hence, option (b).

» Your doubt will be displayed only after approval.


Doubts


Feedback

Help us build a Free and Comprehensive Preparation portal for various competitive exams by providing us your valuable feedback about Apti4All and how it can be improved.


© 2024 | All Rights Reserved | Apti4All