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Problem solving

This topic has 0 member replies
truongvi1982 Newbie | Next Rank: 10 Posts Default Avatar
Joined
19 Nov 2017
Posted:
1 messages
Test Date:
02 Mar 2018
Target GMAT Score:
750

Problem solving

Post Wed Jan 03, 2018 3:41 am
If the circle with center O has area 9\piπ, what is the area of equilateral triangle ABC?
ttps://postimg.org/image/9mlrlj6r9/" target="_blank">

I got r = 3 --> d= 6 = AD
I tried to solve the problem by calculating CD based on the ratio of a 30-60-90 triangle
DC: AD:AC = 1:$$\sqrt{3}$$:2
AD = d = 6 --> DC = 6/$$\sqrt{3}$$
As 2DC = BC --> BC = 2 x 63 = 12$$\sqrt{3}$$
Area of ABC = (BC x AD) / 2 = (12$$\sqrt{3}$$ x 6) / 2 = 36$$\sqrt{3}$$

Sorry that I am totally newbie and don't know how to transfer the square root symbol correctly to my post. And moreover, I don't know why I got this wrong. Can someone help? Thank you very much!

_________________
Vi

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