A and B start together from the same point on a walking watch round a circular course. After 1/2 an hour A has walked three complete circuits and B four and a half. Assuming that each walks with uniform speed, find when B overtakes A.

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15min

18min

22min

20min

answer is D.

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Detailed Solution

Concept- Speed is a measurement of how quickly something is moving at a specific moment in time. It has a scalar value. It measures in m/s. The speed is referred to as uniform speed when a body travels the same distance in the same amount of time. A body is considered to be moving at a non-uniform pace when it travels uneven distances in intervals of time. The ratio of a body's total distance traveled to its entire time traveled is known as its average speed.
Average speed =Total distance traveledTotal time taken
∵ A completed 3 rounds in 12 hours i.e. A complete 3 rounds in 30 min.
∴ Distance traveled by him in 1 minute = 330
=110 of the circuits
∴Distance traveled by B in 1 minute =92130=320 of the circuit
Let after ‘t’ minutes B overtakes A
3t20−t10=1

t=20
Hence, the correct option is 4) 20 min.

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