Math CentralQuandaries & Queries


Question from Wafa, a student:

May Lee bought a cake which is circular in shape. Her sister ate a quarter of the cake. Given that the area of the top surface of the remaining portion is 520 square cm, find the diameter of the cake.

Hi Wafa,

I assume that May Lee's sister cut her quarter of the cake by removing a wedge as in the photo below. In the photo only about an eighth is removed.


What remains is 3/4 of the cake so if the top surface area of 3/4 of the cake is 520 sq cm what is the top surface area of 1/4 of the cake? What is the top surface area of the entire cake?

The area od a circular disk is π r2 sq cm where r is the radius in centimeters. What is the radius of the cake? What is its diameter?


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