Multiple choice

Two pipes A and B can fill a tank in 60 minutes and 75 minutes, respectively. There is also an outlet C. If A, B and C are opened together, the tank is full in 50 minutes. How much time will be taken by C to empty the full tank?

  1. 100 minutes

  2. 110 minutes

  3. 120 minutes

  4. 125 minutes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Rate of A = 1/60, Rate of B = 1/75. Combined rate (A+B) = 1/60 + 1/75 = (5+4)/300 = 9/300 = 3/100. Let C's rate be x. (A+B-C) = 1/50. So 3/100 - x = 1/50, which means x = 3/100 - 2/100 = 1/100. C takes 100 minutes.

AI explanation

Using the net work formula, the combined rate of pipes A, B, and C is (1/60) plus (1/75) minus (1/C), which equals the overall filling rate of 1/50 per minute. Finding a common denominator of 300, the equation becomes (5/300) plus (4/300) minus (1/C) equals 6/300. Solving for the reciprocal of C gives 3/300, meaning C takes 300/3, which is 100 minutes to empty the tank.

Keep practicing — related questions