Question

Pipe A can fill a tank in 36 min and Pipe B can fill a tank in 45 min. Both pipe opened together. Pipe A is closed after x min. Total time taken to fill the tank is 30 min. Find the value of x.
1. 12 min
2. 15 min
3. 10 min
4. 24 min
5. 20 min

Answer 1

Correct Answer - Option 1 : 12 min

Given:

Tank filled by A = 36 min

Tank filled by B = 45 min

Total time taken to fill the tank = 30 min

Formula used:

Efficiency × Time taken = Total capacity of tank

Calculation:

LCM OF 36 and 45 = 180 unit = Total capacity of tank

Time taken by A to fill the tank = 180/36 = 5 unit

Time taken by B to fill the tank = 180/45 = 4 unit

Pipe A is closed after x times but Pipe B is opened for 30 mins

Tank filled by Pipe B = 30 × 4 = 120

Remaining units to be filled = 180 – 120 = 60 units

Remaining 60 units was filled by pipe A

Time taken by Pipe A = 60/5

⇒ 12 min

∴ The value of x is 12 min