A semicircle is half a circle and a quarter circle is a quarter of one, so the area is easy: work out the whole circle, then divide by 2 or by 4. The perimeter is where the marks go. Cutting a circle in half opens up a straight edge, so a semicircle's perimeter is the curved arc PLUS the diameter — it is not half the circumference. A quarter circle closes with two straight radii instead. Always do the whole circle first, then divide, then add the straight edges back on.
Sign up free to see the worked example
A free parent account opens every Learn lesson, with worked examples, plus free practice in every topic and Test 1 of every skill. No card needed, and nothing expires.
Create a free account or sign in