Joe is 1.6m tall. His shadow is 2m long when he stands 3m from the base of a floodlight.
height
1.6 m
2m
3m
What is the height of the floodlight?
2.4 m 2.6 m 4.0 m 4.2 m
You can draw two similar right triangles with this ratios:
x / (2 + 3) = 1.6 / 2
This is: the height of the floodlight is to the length of shadow + the distance of Joe from the foodlight, as the height of Joe is to the length his shadow.