Question Circles and curved boundaries
A figure is made of a circle and a -circle. If AB=10 cm is the diameter of the small circle, find the total shaded area in terms of \pi.
Answer
\boxed{50\pi cm^2}.
Find the space inside a circle shape or the distance around its boundary.
In this one. Use the same length AB in two roles: it is the large radius but the small diameter, then find the shaded area by subtracting the circular hole from the 3/4-circle.
'Area' asks for square centimetres from the radius. 'Circumference' or 'perimeter' on a curved edge asks for plain centimetres from the diameter instead.
Children give a circumference answer in square units, or find a circle's area without squaring the radius first, mixing up the two kinds of measurement.
Worked examples of all 33 patterns and skills, in a booklet you can print.