Difference between revisions of "2007 AMC 12B Problems/Problem 3"

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The point O is the center of the circle circumscribed about triangle ABC, with <BOC = 120° and <AOB = 140°, as shown. What is the degree measure of <ABC?  
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==Problem==
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The point <math>O</math> is the center of the circle circumscribed about triangle <math>ABC</math>, with <math>\angle BOC = 120^{\circ}</math> and <math>\angle AOB = 140^{\circ}</math>, as shown. What is the degree measure of <math>\angle ABC</math>?
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A. 35 B. 40 C. 45 D. 50 E. 60
 
A. 35 B. 40 C. 45 D. 50 E. 60
  
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==Solution==
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<math>\angle AOC=360-140-120=100=2\angle ABC</math>
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<math>\angle ABC=50 \Rightarrow \mathrm {D}</math>
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==See Also==
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{{AMC12 box|year=2007|ab=B|num-b=2|num-a=4}}

Revision as of 09:07, 17 October 2007

Problem

The point $O$ is the center of the circle circumscribed about triangle $ABC$, with $\angle BOC = 120^{\circ}$ and $\angle AOB = 140^{\circ}$, as shown. What is the degree measure of $\angle ABC$?


An image is supposed to go here. You can help us out by creating one and editing it in. Thanks.


A. 35 B. 40 C. 45 D. 50 E. 60

Solution

$\angle AOC=360-140-120=100=2\angle ABC$

$\angle ABC=50 \Rightarrow \mathrm {D}$

See Also

2007 AMC 12B (ProblemsAnswer KeyResources)
Preceded by
Problem 2
Followed by
Problem 4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
All AMC 12 Problems and Solutions