Question

Three taps x, y and z are can fill an empty tank in 20 mins, 30 mins and 40 mins, If all taps are opened and tap y and z got closed after 6 mins then total what time take to fill the tank?
1. 10 mins
2. 11 mins
3. 13 mins
4. 15 mins

Answer 1

Correct Answer - Option 3 : 13 mins

Give:

Three pipe x, y and z are the inlet pipe can fill an empty tank in 20 mins, 30 mins and 40 mins

Concept used:

Work = Time × Efficiency

Time ∝ 1/Efficiency

Calculation:

The efficiency of x is

⇒ 1/20

The efficiency of y is

⇒ 1/30

The efficiency of z is

⇒ 1/40

They started the work and worked for 6 min

⇒ 6 × (1/20 + 1/30 + 1/40)

⇒ 6 × (6 + 4 + 3)/120

⇒ 13/20

Remaining work is

⇒ 1 - 13/20 = 7/20

Time = Work/Efficiency

⇒ (7/20)/(1/20)

⇒ 7 mins

Total time taken

⇒ 6 + 7 = 13 mins

∴ The Total time taken to full the tank is 13 mins