Today we brainstormed ways to calculate the area of a circle. Ms. Gesner was very impressed by the depth of the thinking.
Ways to calculate area of a circle
1. Use the formula. A = ∏ r^2 (Area equals pi times the radius squared. Area equals pi times radius, times radius)
2. Use gridpaper.
3. Use the "Egyptian method"
Here is one way to do it (There are several similar methods).
Draw a square around the circle with sides equal to the diameter
Divide the circle into 9 equal squares
Connect the dots to draw an octagon
Calculate the area of the octagon.
4. Use the Lucas pizza pie triangle method.
Divide the circle into 8 slices.
Use the formula for area of a triangle (A = b x h /2) to caculate the area of each slice
5. Use the "lazy parallelogram" method.
Cut the circle into 8 slices. Make a parallelogram. The area of a parallelogram = b x h (not side times side... you must use the height of the parallelogram)
Homework:Finish all examples on sheet "4.3 Circumference of a Circle"
