Question

A car moves for half of its time at 80km/ hr and for rest of time at40km/hr .If total distance covered is 60km/hr the average speed of the car is

Answer 1

given v1=80km/h, v2=40km/h, distance=60km
we know that
average speed=(v1+v2)/2
=(80+40)/2, =120/2, =60km/h

Answer 2

total distance =60 km
half.distance= 30km

1 st half-
distance=30km
speed - 80 km/h
t=d/s
=30/80
=3/8h

2nd half
d-30km
s=40km/h
t=d/s
=30/40
=3/4

total time = 3/8+3/4= 9/8= 1.125h

avg. speed = t.d./t.t.
=60/1.125
=53.3 km/h