algebra
posted by sushmitha .
a man 6.2 feet tall stands 12 feet away from a streetlight and casts a 5 ft shadow.
How tall is the streetlight?

Draw a little sketch to convince yourself that the shadow of the light is 12'+ 5'=17'
Use proportions and cross product:
6.2 ft : 5 ft shadow
? ft : 17 ft shadow
height of light
= 6.2*17/5
= 21.08'