Question

A metal washer is made by cutting out a circle 13.2 mm in diameter from a larger circle. To the nearest tenth, what is the area of the washer?

Answer 1

The area of the washer will be found by calculating the area of the shaded part.
Area of larger circle:
A=πr²
r=4.4+(13.2/2)=11 mm
thus
A=π×11²=380.13

Area of the small circle:
A=π×(13.2/2)²=136.85 mm

The area of the washer will be:
380.13-136.85
=243.28
~243.3 mm²