Mark costs a shadow that is 4-feet long. At the same time, a nearby tree costs a shadow that is 20-feet long. If mark is 6 feet tall, how tall is the tree?
For this problem we can use ratios 6:4 and x:20. We can also write these ratios as fractions 6/4 and x/20 or 3/2 and x/20. Set the two fractions equal to each other and solve for x:
