Hello!
We use different formulas to calculate the areas of different shape.
RECTANGLE:
To find the area of a rectangle, we must simply multiply its length by its width. The formula for its area is:
A = l × w
SEMICIRCLE:
Since the formula for a circle is pi × r × r, we must use the same formula but divide it in half, because a semicircle is a half circle, which is why its area would also be half of a circle's. The formula for a semicircle's area is:
A = 1/2 pi × r × r
Tip:
Write these formulas down and memorize them so that you don't forget them. You'll have to use these formulas quite often when finding the area of these shapes.