1.

A car travels from A to B at a speed of 20 km h-and returns at a speed of 30 km h-'. The averagespeed of the car for the whole journey is(A) 5 km h-(B) 24 km h-(C) 25 km h-(D) 50 km h-10.

Answer»

C) is the correct answer is

( d). 50 is the correct answer

Hii frnd..

the speed average is

Total average speed is simply = Total distance/Total timeLets say,D = distance travelled by the car in EACH directiont1 = time spent on onward tript2 = time spent on return tripThus, the total distance travelled by the car = D+D= 2DAnd, by the formula, Speed = Distance/TimeS1 = D/t1 => t1 = D/S1S2 = D/t2 => t2 = D/S2Total average speed = Total Distance/Total time = 2D/(t1+t2) = 2D/(D/S1+D/S2) = 2S1*S2/(S1+S2)

Remember this general formula for a total average speed problems:Total average speed = 2S1*S2/(S1+S2)

So in the question S1 = 20km/hr

&S2 = 30km/hr

So av. speed = 2 x 20 x 30/20+30

= 24km/hr

24km / hr is the right answer

please accept best

25 is the right answer

option b is right answer



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