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
40 km/h. What is the average speed for Abdul’s trip?

Answer 1

Answer:

26.666km/h (approx)

Step-by-step explanation:

Let distance from home to school be x.

S=D/T

20=x/t

x=20t

t=x/20

On return drive

40=x/t

t=x/40

Avg speed=total d/total t

=2x/x/40+x/20

=2x/3x/40

=80x/3x

=80/3

=26.666km/h(approx.)

Answer 2

Answer:

Step-by-step explanation:

The average speed for the return trip is:

v = 2L/(t1+t2)

v average speed

L one way distance

t1 time taken to drive to school

t2 time taken to drive back home

Now:

t1 = L/20

t2 = L/40

Hence:

V = 2L/(L/20+L/40) = 2/(1/20+1/40) = 26.7 km/hr.

Average speed is about 27 km/hr.

Note that the average speed is not the numerical average of 20 and 40. The driver spends more time going to school than on the way back. Therefore the average speed is closer in value to the lower velocity.