5 taps are connected to a tank among which 3 taps (A, B and C) are inlet taps and 2 taps (P and Q) are outlet taps. A, B and C can fill the tank in 24 minutes, 30 minutes and 36 minutes respectively while taps P and Q can empty the tanks in 15 minutes and 45 minutes respectively. If tap B is opened after 5 minutes and tap P is opened 5 minutes after tap B, find the time taken to fill the tank completely.
5 taps are connected to a tank among which 3 taps (A, B and C) are inlet taps and 2 taps (P and Q) are outlet taps. A, B and C can fill the tank in 24 minutes, 30 minutes and 36 minutes respectively while taps P and Q can empty the tanks in 15 minutes and 45 minutes respectively. If tap B is opened after 5 minutes and tap P is opened 5 minutes after tap B, find the time taken to fill the tank completely. Correct Answer 36 minutes
Tap A can fill the tank in 24 minutes
⇒ In 1 minute tank filled with A = 1/24
Tap B can fill the tank in 30 minutes
⇒ In 1 minute tank filled with B = 1/30
Tap C can fill the tank in 36 minutes
⇒ In 1 minute tank filled with C = 1/36
Tap P can empty the tank in 15 minutes
⇒ In 1 minute, it can empty 1/15 part of tank.
Tap Q can empty the tank in 45 minutes
⇒ In 1 minute, it can empty 1/45 part of tank.
Initially tap A, C and Q are opened for 5 minutes
⇒ Tank filled in first 5 minutes = 5 × (1/24 + 1/36 – 1/45)
⇒ 5 × (5/72 – 1/45) = 85/360
Tap B is also opened for next 5 minutes.
So, the tank filled in next 5 minutes = 85/360 + 5 × 1/30
⇒ 145/360
Tank filled in first 10 minutes = 85/360 + 145/360 = 23/36
Now, tap P is also opened
Effective filling of tank in 1 minute = (1/24 + 1/30 + 1/36) – (1/15 + 1/45)
⇒ 37/360 – 32/360
⇒ 5/360 = 1/72
We need to fill 13/36 part of tank now
It will take 26 minutes more to fill the tank completely.
Total time taken to fill the tank completely = 5 + 5 + 26 = 36
∴ 36 minutes is required to fill the tank completely.