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In the figure above, O is the center of the circle. If AB = 10, what

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Math Expert
Joined: 02 Sep 2009
Posts: 50007
In the figure above, O is the center of the circle. If AB = 10, what  [#permalink]

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21 Nov 2017, 23:13
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93% (00:58) correct 7% (00:52) wrong based on 43 sessions

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In the figure above, O is the center of the circle. If AB = 10, what is the area of the circle?

(A) 10π
(B) 20π
(C) 25π
(D) 50π
(E) 100π

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2017-11-21_1032_001.png [ 7.42 KiB | Viewed 596 times ]

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Joined: 15 Aug 2016
Posts: 85
In the figure above, O is the center of the circle. If AB = 10, what  [#permalink]

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22 Nov 2017, 03:49
Since <AOB=60 and AO=BO(Radius of the circle)
=> <OAB+<ABO+<AOB=180
=> 60+<OAB+<ABO=180
But since AO=BO this means <OAB=ABO (opposite angles are equal if opposite sides are equal).
=><ABO=<OAB=60
=>AO=10 which is the radius of the circle.
=> Area= pi*r*r=10*10*pi=100 pi.
Intern
Joined: 29 Aug 2016
Posts: 33
Re: In the figure above, O is the center of the circle. If AB = 10, what  [#permalink]

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22 Nov 2017, 05:50

The Triangle is equilateral. Radius is 10.

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Re: In the figure above, O is the center of the circle. If AB = 10, what &nbs [#permalink] 22 Nov 2017, 05:50
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