(c) Anthony K. Grafton 2003

How Tall is that Tree?

How good are you at guessing the height of a tree? People who cut down trees need to know just how tall they are so they will know if they will hit anything on the way down. Did you know that you can use your own shadow to measure the height of a tree? All you need is a sunny day, a ruler, and a little math.

First you need to know how tall you are in inches. Then, go outside and, maybe with the help of a friend, measure the length of your shadow in inches. Divide your height by the length of your shadow, and write down the number you get. Next, at the same time of day, measure the length in inches of the shadow cast by a tree in your yard. Multiply that length by the number you wrote down before. The result is the height of the tree in inches. To get the height in feet, divide that number by twelve. That’s all!

So, let’s say Karlea is 48 inches tall. Karlea goes outside on a sunny day and finds out her shadow is 22 inches long. She divides 48 by 22 and gets 2.2, which she writes down. Then Karlea measures the length of the shadow of a tree in her back yard and gets 152 inches. Karlea multiplies 152 by 2.2 and gets 334 inches as the height of the tree. Last, Karlea divides 334 by 12, and finds out that her tree is almost 28 feet tall!

How tall are the trees in your yard? How much taller will they be by the end of next summer?