Time = distance/rate
let the equal distances be x km
individual times are:
x/20, x/60, and x/120 hours
total time = x/20 + x/60 + x/120
= (6x/120 + 2x/120 + x/120)
= 9x/120 hrs
avg speed = total distance/total time
= 3x / (9x/120)
= 40 km/h
suppose a car is driven from town A to town B from town B to town C and from town C to town D which have equal distances at average speeds 20km/hr,60km/hr and 120km/hr respectively,what is the average speed for the whole journey
1 answer