What is the area of a ring with an outer diameter of 90 inches and an inner diameter of 80 inches?
- 325 * pi
- 425 * pi
- 435 * pi
Explanation from PART66Online
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.
S
syazaraehah asked · 4 Jul 2013
how to solve it
Community Comments (3)
P
PART66Online
4 Jul 2013
Calculate area of circumference with diameter 90 inches then subtract from result area of circumference with diameter 80 inches.
R
rommarioo
16 Nov 2017
if so, then A = 1700pi
P
PART66Online
19 Nov 2017
rommarioo, please go for math lessons, you are wrong.
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