A car travels at a speed of 80 km/h during the first half of its running time and at 40 km/h during the other half. Find the average speed of the car. (60 km/h)

Explanation

Let the total running time = x hrs
Speed in the first half of its running time i.e., `x/2` hrs = 80 km/h
`therefore` Distance covered in `x/2` hrs = `80xxx/2=(80x)/2=40xkm`
Speed in second half its running time = 40 km/h
`therefore` Distance covered in `x/2hrs" "40xxx/2=20xkm`
Total distance = 40x + 20x = 60x km
Total time = `x/2+x/2=xhrs`
`therefore` Average speed = `("Total distance")/("Time")=(60x)/x=60km//hr`