Art of Problem Solving

2014 AMC 10B Problems/Problem 19: Difference between revisions

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==Solution==
==Solution==
Pick any arbitrary point on the circle and it is clear that 120 degrees of the circle is possible for the second point. Therefore the probability is <math>120/360=1/3</math>


==See Also==
==See Also==
{{AMC10 box|year=2014|ab=B|num-b=18|num-a=20}}
{{AMC10 box|year=2014|ab=B|num-b=18|num-a=20}}
{{MAA Notice}}
{{MAA Notice}}

Revision as of 16:56, 20 February 2014

Problem

Two concentric circles have radii $1$ and $2$. Two points on the outer circle are chosen independently and uniformly at random. What is the probability that the chord joining the two points intersects the inner circle?

$\textbf{(A) }\frac{1}{6}\qquad\textbf{(B) }\frac{1}{4}\qquad\textbf{(C) }\frac{2-\sqrt{2}}{2}\qquad\textbf{(D) }\frac{1}{3}\qquad\textbf{(E) }\frac{1}{2}\qquad$

Solution

Pick any arbitrary point on the circle and it is clear that 120 degrees of the circle is possible for the second point. Therefore the probability is $120/360=1/3$

See Also

2014 AMC 10B (ProblemsAnswer KeyResources)
Preceded by
Problem 18
Followed by
Problem 20
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 10 Problems and Solutions

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