a motorcyclist drives from A to B with a uniform speed of 30km/ hr and returns back with a speed of 20km/hr.find its average speed
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Let distance between A and B is D
Then, time taken by motorcyclist with uniform speed 30 km/h ,T₁ = distance/speed = D/30 hrs
Again, they return with uniform speed 20 km , so time taken by motorcyclist , T₂ = D/20 hrs
Now, average speed of motorcyclist = total distance/total time taken
= (D + D )/(D/30 + D/20) km/h
= 2 × 30 × 20/(30 + 20) km/h
= 24 km/h
Then, time taken by motorcyclist with uniform speed 30 km/h ,T₁ = distance/speed = D/30 hrs
Again, they return with uniform speed 20 km , so time taken by motorcyclist , T₂ = D/20 hrs
Now, average speed of motorcyclist = total distance/total time taken
= (D + D )/(D/30 + D/20) km/h
= 2 × 30 × 20/(30 + 20) km/h
= 24 km/h
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