Question

The diameter of the larger circle is 10.5 cm. The diameter of the smaller circle is 4.5 cm. What is the approximate area of the shaded region?

Answer 1

Area of the shaded region=area of the larger circle - area of the smaller cirlce.

1) we calculate the area of the larger circle.
diameter=10.5 cm
radius=diameter / 2=10.5 cm/2=5.25 cm
area=πr²=π(5.25 cm)²=27.5625π cm²

2) we calculate the area of the smaller circle:
diameter=4.5 cm
raduys=diameter / 2=4.5 cm/2=2.25 cm
area=πr²=π(2.25 cm)²=5.0625π cm²

3) we calculate the area of the shaded region.
area of the shaded region=27.5625π cm² - 5.0625π cm²=22.5π cm².
22.5π cm²=22.5(3.141592654...) cm²≈70.69 cm²

Answer : 22.5π cm²          or 70.69 cm²