a motorcyclist drive from A to B with a uniform speed of 8 km per hour and returns back with the speed of y km perhour find its average speed.
ArindamSinghArie:
What is the time taken to traverse the distance between A&B and B&A?
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Let distance between A and B = P km
we know,
time = distance/speed
when motorcyclist drive from A to B with speed 8 km/h then,
time = P/8 hours
when motorcyclist drive from B to A with speed Y km/h then ,
time = P/Y hours
av speed = total distance/total time .
av speed = { P + P }/{ P/8 + P/Y}
= {2P}/P( 8 + Y)/8Y
=16Y/( 8 + Y) km/h
hence, average speed = 16Y/( 8 + y) km/h
we know,
time = distance/speed
when motorcyclist drive from A to B with speed 8 km/h then,
time = P/8 hours
when motorcyclist drive from B to A with speed Y km/h then ,
time = P/Y hours
av speed = total distance/total time .
av speed = { P + P }/{ P/8 + P/Y}
= {2P}/P( 8 + Y)/8Y
=16Y/( 8 + Y) km/h
hence, average speed = 16Y/( 8 + y) km/h
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