How many times do the hands of a clock coincide in 5 hours ?
A. 5
B. 4
C. 6
D. 3
Answer : B. 4
Explanation:
Hour hand and minute hand coincide every 65:5 minute, so in 5 hour they will coincide 4 times The hour hand covers 2*360 degrees in 24 hours, i.e 1440 minutes. So, in one minute, it covers 1440/720 = 1/2 degree.
Difference in angular distance travelled by the minute hand and the hour hand in one minute is thus 6-1/2 = 11/2 degrees. So, on a full rotation (360ᵒ), any similar event between them will be repeated every 360/(11/2) = 65 5/11 minutes.
