A farmer wants to measure the distance across a river on his farm. One morning, he notices that the shadow of a tree on one bank falls directly across the river so that the tip of the shadow just touches the opposite
bank. At the same instant, he measures the length of the shadow to a nearby fence post and finds it to be
3.75 m. He knows the tree is 12 m tall and the post is 2 m tall How wide is the river?