What is the area of a ring with an outer diameter of 90 inches and an inner diameter of 80 inches?
- 435 * pi
- 425 * pi
- 325 * pi
Explanation
A ring's (annulus) area is pi*(R^2 - r^2) using the two radii. The radii are half the diameters: R = 45 in and r = 40 in, so R^2 - r^2 = 2025 - 1600 = 425, giving 425*pi square inches. Using diameters instead of radii would give the wrong values.
syazaraehah asking:
how to solve it
Community Comments (3)
D
dimky Posts: 514 04.07.2013 / 12:09
Calculate area of circumference with diameter 90 inches then subtract from result area of circumference with diameter 80 inches.
R
rommarioo Posts: 3 16.11.2017 / 22:40
if so, then A = 1700pi
D
dimky Posts: 514 19.11.2017 / 14:28
rommarioo, please go for math lessons, you are wrong.
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