B.ed Exam Numerical Ability Time Distance and Speed

The circumference of the front wheels of a locomotive is 3.5 m and that of the back wheels is 3.0 m .If the locomotive is moving at a speed of 15 m/sec ,the shortest time in which both wheels will make a whole number of turns is ,in sec?

Read Solution (Total 1)

1.4 sec.

Front wheel completes 1 revolution in 3.5/15=7/10 sec.
Back wheel completes 1 revolution in 3/15=1/5 sec.
So minimum time to complete a whole number of turns=LCM (7/10, 1/5) = 7/5 = 1.4 sec.
In 1.4 sec front wheel makes (7/5)/(7/10)=2 revolutions and
back wheel makes (7/5)/(1/5)=7 revolutions.
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