If the woman is 180 cm tall, how high is the streetlight in meters and in feet?

Question

This is from Chapter 4, Exercise 4-4, #16 of Fundamentals of Technical Mathematics (2nd edition): The shadow of a woman standing 11 m from a streetlight is 1.5 m long. If the woman is 180 cm tall, how high is the streetlight in meters an in feet?

Answer 1

The ratio of the woman's height to her shadow is the same as the ratio of the streetlight height to the distance between the streetlight and the end of her shadow, ie:

A = woman's height = 1.8m
B = shadow length = 1.5m
C = streetlight height
D = distance from streetlamp to woman = 11m

A/B = C/(D+B)
i.e. C = (D+B)*A/B = 15m