Circle area and perimeter questions

A semicircle of diameter 20 centimetres sits on top of a square of side 20 centimetres. Here's the square. And the semicircle sits on its top side. Find the total area of the figure. Take pi as three point one four. Try it first. Pause if you like. Two different shapes stick together on one side. This question has been done before. Previously, the question wanted the perimeter, so we look at the sides outside. Now, take note, this question is asking for area. Perimeter is how far round. Area is how much is inside. So the edge where the square and the semicircle meet doesn't change anything this time. Now, area uses the radius. But this question gives us 20, and that's the diameter, right across the circle. The radius is half of the diameter. So here's the rule for the area of a circle. The square first. Given that 4 sides of a square are of the same length, the area of a square is length times breadth. So it's 20 times 20. That's four hundred square centimetres. Now the curved piece. The diameter is 20. So the radius is 10. The area of a semicircle is a half, times pi, times the radius, times the radius. Half, times three point one four, times 10, times 10. That's one hundred and fifty seven square centimetres. When two shapes stick together, we add their areas up. So the total area of the figure is the area of the square, plus the area of the semicircle. four hundred square centimetres and one hundred and fifty seven square centimetres gives five hundred and fifty seven square centimetres. We have one same figure, asking for either perimeter or area. If it's asking for perimeter, remember we do not include the edge where the 2 shapes meet. If it's asking for area, everything inside a joined figure is included. So read the question, and know which one it wants.