Question

At a certain time of day, a tree 15 m tall cast a shadow of 12 m, while a second tree cast a shadow of 20 m. How tall is the second tree?

Answer 1

25 metres tall.

Explanation:

The heights of the trees are directly proportional to the length of their shadows because at the same time of day, the sun will be at the same angle in the sky.

The trees and their shadows form 2 similar triangles:
Write as a proportion:

heightshadow x20=1512

12x=20×15

x=20×1512

x=25 metres tall.

As check: find the constant for each tree:

1512=1.25 and 2520=1.25

i hope this help