Question

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

Answer 1

25 kmph because average is found by adding 20 and 30 together which is 50 and dividing that by 2. Which gives us the answer 25 kmph

Answer 2

We can calculate the average speed in two

ways


Method -1

Distance in both cases in the same

So average speed is the average of two

speeds.

That is 20+30 / 2 = 25 km/h


Method -2

First speed = 20 km/h

Second speed = 30 km/h

With these speeds the least possible common

distance we can travel is 60 km (LCM 20,30)

With speed 20 km/hr the time required to

complete the journey is 3 hr

With speed 30 km/h the time required to

complete the journey is 2 hr

Average speed = Total distance / total time

Total distance = 60 + 60 = 120 (as same paths

are used)

Total time = 3 he + 2hr = 5hr

Therefore average speed = 120/5

= 25 km/h


In these ways we can solve the problem .

Choose which you think is easy..