There are 3 pipes A,B and C that when opened simultaneously would fill a tank…
2024
There are 3 pipes A,B and C that when opened simultaneously would fill a tank in 20 minutes. C can fill the tank twice as fast as A which in turn would fill the tank twice as fast as B. How long will it take for B alone to fill the tank ?
- A.
140 min
- B.
120 min
- C.
70 min
- D.
35 min
Attempted by 11 students.
Show answer & explanation
Correct answer: A
Let b be the time (in minutes) for pipe B alone to fill the tank.
Rates (tank per minute): B = 1/b. A fills twice as fast as B, so A = 2/b. C fills twice as fast as A, so C = 4/b.
Combined rate = 1/b + 2/b + 4/b = 7/b.
They fill the tank together in 20 minutes, so combined rate = 1/20.
Set 7/b = 1/20 and solve: b = 7 × 20 = 140 minutes.
Answer: B alone takes 140 minutes to fill the tank.