Question

A car travels along a straight line for the first time with speed 40km/h and the second half time with speed60km/h . find average speed of the car.

Answer 1

let the total distance travelled by the car be 2x
time taken by car for first half of journey, t1 = x/40 hr
also, time taken for second half, t2 = x/60 hr
Total time taken = t1 + t2 = x/40 +x/60 = 5x/120 hr
avg. speed = total distance/total time = (2x)/(5x/120) = 48 km/hr
hence ans is 48 km/hr.