 This video is talking about solving problems using similar triangles. And in particular we're going to use similar triangles to solve this word problem. So Carl is measuring the height of a pine tree that he was standing next to by comparing it to his height using the length of his shadow and the tree's shadow. Carl is 6 foot 2 inches tall and his shadow is 2 feet 6 inches tall. The tree has a shadow of 32 feet long and we want to find the height of the pine tree. So it helps to draw a little picture. So here's a pretty cruddy picture. Here we have Carl and here we have a tree. And then there's shadows that are sort of laid upon the ground. So we know that Carl is 6 foot 2 and his shadow is 2 foot 6 inches long. So 6 feet is the same as 72 inches because there are 12 inches in a foot. So therefore 6 foot 2 is 74 inches. So Carl is 74 inches tall. His shadow is 2 feet 6 inches long which is 12 times, sorry, 2 times 12 plus 6. The length of the shadow on the ground is 32 feet but the height of the tree is unknown. So let's call that x. So we'll set up our proportions. Carl divided by tree. And now Carl's height is known but the tree's height is unknown. We'll use the ratio of shadows as the known ratio. Carl's shadow is 30 inches long. The shadow of the tree is 32 feet long. And so since these two triangles are similar, we now have a proportion that we can solve using cross multiplication. We have 30 times x is equal to 72 times 32. And so our final answer is 76.8 feet and that's how tall the tree is. By the way, I made a mistake in this video. 72 isn't correct. Go talk to your teacher. Maybe they'll give you some extra credit for finding that and fixing that mistake.