Question

rajat covered a straight line distance between two states in three parts. he coverd the 1/4 th the distance of speed 20 km/hr. he coverd the 1/6 th of the remaining distance at the speed of 35 km/hr and the rest of distance at 40km/hr. what will be avaerage speed for the whole journey?

Answer 1

Answer:

               Average Speed = 31.54 km / hr

Step-by-step explanation:

Let the total distance = x km

We know that

Distance = Speed × Time

⇒ Time = Distance/Speed

Case 1:

Time = Distance/Speed

Time = (x/4)/(20) =  x/80

Remaining distance = x - x/4 = 3x / 4

Case 2:

1/6 th of 3x/4 = (1/6)(3x/4) = 3x/24 = x/8

Time = Distance/Speed

Time = (x/8)/(35) = x/280

Remaining distance = 3x/4 - x/8 = 5x / 8

Case 3:

Time = Distance/Speed

Time = (5x/8)/(40) = x/64

Total time = x/80 + x/280 + x/64 = x(1/80+1/280+1/64) = 0.0316 x

We know that

Average Speed = Total Distance/Total Time

Average Speed = (x)/(0.0316 x) = 31.54 km / hr

Average Speed = 31.54 km / hr