Question

When a 5-foot vertical pole casts a 3-foot 4-inch shadow, an oak tree casts a 20-foot shadow. Find the height of the tree in feet?

Answer 1

First, express the measures in inches,

Since 1 ft=12 inches:

5 ft = 60 inches

3 ft and 4 inches = 40 inches

20 ft= 240 inches

This is a proportion problem, we have to use the ratio :

object height to shadow length

5 / 3 and 4 inches = 60 /40

x / 240

Where x is the height of the tree:

60/40 = x/240

Solve for x:

60/40 (240) = x

360 inches = x

360 inches = 30