Hello! So Brian is 6 feet tall and casts a 4 foot shadow and the tree’s shadow is 20 feet. To find the height of the tree, we can write and solve a proportion. Set it up like this:
6/4 = x/20
This is because we are looking for the height of the tree, and having it set up like this will help us get to the right answer. Let’s cross multiply. 6 * 20 is 120. 4 * x is 4x. That simplified to 120 = 4x. Now, divide each side by 4 to isolate the x. 4x/4 cancels our. 120/4 is 30. Let’s cross multiply to check out answers. 6 * 20 is 120. 30 * 4 is 120. 120 = 120. There. x = 30. The tree is 30 feet tall.