2016 · Q37
A tank can be filled by pipe X in 2\ {h} and pipe Y in 6\ {h}. At 10 am, pipe X was opened. At what time will the tank be filled if pipe Y is opened at 11\ {am} ?
Elementary MathematicsTime and Work
- A12:45 hours
- B5:00 p.m.
- C11:45 a.m.
- D11:50 a.m.
Explanation
Pipe X fills 1/2 of the tank per hour, so by 11 am half the tank is full. From 11 am both pipes fill at 1/2+1/6 = 2/3 per hour, and the remaining half takes (1/2)/(2/3) = 3/4 h = 45 min. The tank is full at 11:45 am (option C).