Question #9de8c

1 Answer
Daniel W.
Apr 17, 2016

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)

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