Use geometry to determine the area of a rectangular piece of cloth. For example, if you need to patch a hole that is 1 inch by 2 inches, how much cloth do you need to use in square inches to patch the hole and have a 1-inch margin to sew it in?
The cloth must be 2 inches by 3 inches, which would require 6 square inches of cloth.
Use geometry to determine the length of a belt, bracelet or cord that is appropriate for the average person. If you want to make a sleeve cuff that fits around an arm that is a cylinder with a diameter of 3 inches, how much cord do you need to go all the way around?
The circumference of a circle is pi * 3 inches, so 9.42 inches.
Use geometry to find the volume of a hat if the hat is a hemisphere and it has a radius of 3 inches.
The volume of the hemisphere is (2 * pi * (3 inches)^3)/3 = 926 milliliters.