Question

Question #9de8c

Answer 1

Average speed, `v = d/ t = (2x) / ((3x)/4) = 8/3 = 2.67 km.hr^(-1)`

Explanation:

Define the distance of A to B as x.

Average speed is total distance divided by total time taken. We already know that since the man walks from A to B and then B to A he travelled a distance of 2x. All we need to calculate is the total time taken.

Calculate the times taken.
A to B: `v = d/t ⇒ t_1 = d_1/v_1 = x / 2`
B to A: `t_2 = d_2/v_2 = x / 4`

Calculate total time and then average speed.
Total time taken, `t = t_1 + t_2 = x/2 + x/4 = (3x)/4`

Average speed, `v = d/ t = (2x) / ((3x)/4) = 8/3 = 2.67 km.hr^(-1)`