17. Five mark example problem III

A boy of height $90 \ cm$ is walking away from the base of a lamp post at a speed of $1.2 \ m/sec$. If the lamp post is $3.6 \ m$ above the ground, find the length of his shadow cast after $4$ seconds.

 

Answer:

 

The length of the shadow of the boy after $4$ seconds $=$  $m$