Question

A man walks at a speed of $6$ km/hr for $1$ km and $8$ km/hr for the next $1$ km. What is his average speed for the walk of $2$ km?

Answer 1

$Speed=6km/h$

$distance=1km$

$Time=\frac{distance}{speed}$

$=\frac{1}{6}h$

case 2

$Speed=8km/h$

$Distance=1km$

$Time=\frac{distance}{speed}$

$=\frac{1}{8}h$

Average speed = Total distance / total time taken

$=\frac{1+1}{\frac{1}{6}+\frac{1}{8}}$

$=\frac{2}{\frac{(4+3)}{24}}$

$=\frac{2}{\frac{7}{24}}$

$=\frac{48}{7}$

$=6.85km/h$