Question

A car travels 50 km at a uniform speed of 100 km/h and the next 40 km at a uniform speed of 80 km / h. find the average speed of the entire journey.

Answer 1

Answer:

90 km/h

Explanation:

d1 = 50 km

s1 = 100 km/h

d2 = 40 km

s2 = 80 km/h

Using, distance = speed × time

t1 = d1/s1 = 50/100 = 0.5 hrs

t2 = d2/s2 = 40/80 = 0.5 hrs

Average speed=Total distance/Total time

Average speed = (d1 + d2) / (t1 + t2)

Average speed = 90 / 1 = 90 km/h

Answer 2

Total time taken = (50/100)+(40/80) hour

                          = (1/2)+(1/2) hour

                          = (1+1)/2 hour

                         =(2/2) hour

                         = 1 hour

Total distance covered = (50+40) km

                                      = 90 km

So, average speed = (distance/time)

                                = (90/1) km/h

                                = 90 km/h