2023 · Q35
Three taps A, B and C together can fill a tank in 6 hours. Tap C alone can fill the tank in 12 hours. To fill the tank, when it is empty, all the three taps are started together. After working t hours, tap C is closed and the tank is filled in 8 more hours. What is t equal to?
Elementary MathematicsTime and Work
- A1
- B2
- C4
- D6
Explanation
With rates a, b, c: a + b + c = 1/6 and c = 1/12, so a + b = 1/12. The work equation is t/6 + 8(a + b) = 1, i.e. t/6 + 8/12 = 1. This gives t/6 = 1/3, so t = 2 (B).