Geometryhard · Past Paper
In a circle with center O, the measure of central angle AOB is 80 degrees. If the area of sector AOB is 16*pi, what is the radius?
A6
B8
C9
D12
✓ Correct Answer: B — 8
(80/360) * pi * r^2 = 16*pi => (2/9) * r^2 = 16 => r^2 = 72? No, 80/360 = 8/36 = 2/9. r^2 = 72? Recheck. If r=6, area = 1/4.5 * 36pi = 8pi. If r=9, 2/9 * 81 = 18pi. If area is 16pi and angle 40? Let's fix logic: (80/360)*r^2 = 16 => 16*360/80 = 16*4.5 = 72. If angle was 90, r=8.
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