Multiple choice

Two pipes P and Q can fill a tank in 8 hours. If only pipe P is open then it would take 4 hours longer to fill the tank. Find how much longer it would take if only pipe Q is open.

  1. 16 hr.

  2. 12 hr.

  3. 10 hr.

  4. 8 hr.

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Combined rate: 1/8 tank per hour. Let P's rate = 1/x, Q's rate = 1/y. Given: P takes 4 hours longer than combined time, so x=12 hours. P's rate = 1/12. Q's rate = (1/8)-(1/12)=1/24. Therefore Q alone takes 24 hours, which is 16 hours longer than the combined 8 hours.

Keep practicing — related questions