1957 AMC 12 Problem 46

Attempt Problem 46 of the 1957 AMC 12 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1957 AMC 12 solutions, or check the answer key.

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46.

Two perpendicular chords intersect in a circle. The segments of one chord are 33 and 4;4; the segments of the other are 66 and 2.2. Then the diameter of the circle is:

89\sqrt{89}

56\sqrt{56}

61\sqrt{61}

75\sqrt{75}

65\sqrt{65}

Answer: E
Concepts:chordcoordinate geometryperpendicular bisector
Difficulty rating: 1870
Small Hint:

Place the chord intersection at the origin and the perpendicular chords on the coordinate axes

Big Hint:

The circle’s center lies on both chord perpendicular bisectors

Solution:

Place the intersection at (0,0)(0,0) with endpoints (3,0),(-3,0), (4,0),(4,0), (0,2),(0,-2), and (0,6).(0,6). The perpendicular bisectors of the chords are x=12x=\frac{1}{2} and y=2,y=2, so the center is (12,2).(\frac{1}{2},2). Using the endpoint (4,0),(4,0), r2=(412)2+(02)2=654. \begin{aligned} r^2 &=\left(4-\frac12\right)^2+(0-2)^2\\ &=\frac{65}{4}. \end{aligned} Therefore the diameter is 2r=65.2r=\sqrt{65}.

Thus, the correct answer is E.

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Problem 46 in Other Years

1950 AMC 12 · 1951 AMC 12 · 1952 AMC 12 · 1953 AMC 12 · 1954 AMC 12 · 1955 AMC 12 · 1956 AMC 12 · 1958 AMC 12 · 1959 AMC 12