Multiple choice

A tank has an inlet pipe and an outlet pipe. • Inlet fills tank in 8 hrs (if outlet is closed) • Together: inlet and outlet fill in 10 hrs • Only outlet open, how long to empty half tank?

  1. 40

  2. 35

  3. 20

  4. 30

  5. 25
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Inlet rate = 1/8. Combined rate = 1/10. Outlet rate = 1/8 - 1/10 = 1/40. To empty the whole tank takes 40 hours. To empty half the tank takes 20 hours.

AI explanation

Using the least common multiple method, assume the total capacity of the tank is 40 units. The inlet pipe fills at 5 units per hour, and the combined rate of the inlet and outlet is 4 units per hour, meaning the outlet empties at 1 unit per hour. To empty half of the tank, the outlet must remove 20 units of water. At a rate of 1 unit per hour, it takes 20 hours.

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