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