Difference between revisions of "1998 AHSME Problems/Problem 11"

(New page: == Problem == Let <math>R</math> be a rectangle. How many circles in the plane of <math>R</math> have a diameter both of whose endpoints are vertices of <math>R</math>? <math> \mathrm{(A)...)
 
 
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== See also ==
 
== See also ==
 
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{{AHSME box|year=1998|num-b=10|num-a=12}}
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Latest revision as of 13:29, 5 July 2013

Problem

Let $R$ be a rectangle. How many circles in the plane of $R$ have a diameter both of whose endpoints are vertices of $R$?

$\mathrm{(A) \ }1 \qquad \mathrm{(B) \ }2 \qquad \mathrm{(C) \ }4 \qquad \mathrm{(D) \ }5 \qquad \mathrm{(E) \ }6$

Solution

There are $6$ pairs of vertices of $R$. However, both diagonals determine the same circle, therefore the answer is $\boxed{5}$.

[asy] size(200); defaultpen(0.8);  pair A=(0,0), B=(5,0), C=(5,2), D=(0,2);  draw ( A--B--C--D--cycle ); draw( circle( (A+B)/2, length((A-B)/2) ), red ); draw( circle( (C+B)/2, length((C-B)/2) ), red ); draw( circle( (C+D)/2, length((C-D)/2) ), red ); draw( circle( (A+D)/2, length((A-D)/2) ), red ); draw( circle( (A+B+C+D)/4, length((A-C)/2) ), green ); [/asy]

See also

1998 AHSME (ProblemsAnswer KeyResources)
Preceded by
Problem 10
Followed by
Problem 12
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All AHSME Problems and Solutions

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