2014 · Q40
At what point of time after 3 o'clock, do the hour-hand and the minute-hand of a clock occur at right angles for the first time?
Elementary MathematicsArithmetic
- A9 o'clock
- B4 hours 37 1/6 minutes
- C3 hours 30 8/11 minutes
- D3 hours 32 8/11 minutes
Explanation
Relative speed 330°/hr; from 90° at 3:00 need 180° more: t = 180/330 hr = 32 8/11 min past 3.