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Tuesday, April 15, 2014

Concentric Circles Problems

Category: Plane Geometry

"Published in Newark, California, USA"

A metal washer 1 in. in diameter is pierced by a ½ in hole. What is the area of one face of the washer?


To illustrate the problem, it is better to draw the figure as follows

Photo by Math Principles in Everyday Life

A metal washer is made from two concentric circles and its a ring shape. 

Let d1 = be the diameter of outer circle
      d2 = be the diameter of inner circle
      A1 = be the area of large circle
      A2 = be the area of small circle
Area of Large Circle:
Area of Small Circle:
Therefore, the area of a metal washer is