Question

Abdul while driving to school computes the average speed for his trip to be 20km per hour. on his return trip along the same route there is less traffic and the average speed is 30km per hour. what is the average speed for abdul's trip?

Answer 1

average speed=total distance÷total time. let the distance from abdul's house to school be x km.
20 km/h = x ÷ t1
while his return trip,
30 km / h = x ÷ t2
t1 = 20 ÷x
t2 = 30 ÷ x
total time = t1 + t2
=20×3 ÷ 3x + 30×2 ÷ 2x
=60 ÷5x =12 ÷ x
total time= 12 ÷x
total distance = x + x =2x
= x ÷ 12 ÷ 2 x =2×12 = 24km/h