Answer:
3.75cm 44.16cm²
20cm 314cm²
42cm 1384.74cm²
Explanation:
Area of a circle = πr²
Where : = π = pi = 3.14
R = radius
the diameter is the straight line that passes through the centre of a circle and touches the two edges of the circle.
A radius is half of the diameter
16. Radius = 7.5 / 2 = 3.75
Area = 3.14 x 3.75² = 44.16
17. Diameter = 10 x 2 = 20
Area = 10² x 3.14 = 314
18. Diameter = 21 x 2 = 42
Area = 21² x 3.14 = 1384.74