Winona Area Public SchoolsMrs. Shields Honors Math class is learning how to calculate the circumference and area of circular objects. The class started with a fun math problem which asked students if buying two 12-inch pizzas for $20 or one 18-inch pizza for $20 is a better deal. By figuring out the area of each pizza and finding the unit rate, they were able to find that the 18-inch pizza gave you the best deal. Mrs. Shields stated ”There is a misconception that the two pizzas would be the better deal, so having the students discuss and calculate helps them to realize that they are not getting a 24 inch pizza, but rather two 12 inch pizzas.”
Students are learning the equation to find the circumference of a circle, which is pi times the diameter of a circle. The circumference of a circle is the distance around the outside which is similar to a perimeter of a square shape. So before finding the circumference of the object, students first had to find either the diameter or radius of the circle. The radius of a circle is the distance from the center of the circle to any point on the circle. The diameter is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. After finding either the radius or diameter, students took pi times the diameter to get the circumference.
After the class lesson, students branched into groups of two and calculated the circumference and diameter of physical circular objects. Cups, plates, tape rolls and cylinders were among some of the objects students were tasked with calculating. Using a fabric tape measure, they measured around the outer edge of each object. This activity helped students apply the concepts and equations they learned in the lesson to physical objects.