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Geometry and Trigonometry Difficulty: Hard

Points Q and R lie on a circle with center P . The radius of this circle is 9 inches. Triangle P Q R has a perimeter of 31 inches. What is the length, in inches, of QR¯?

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Explanation

Choice B is correct. Since it's given that P is the center of a circle with a radius of 9 inches, and that points Q and R lie on that circle, it follows that PQ¯ and RP¯ of triangle PQR each have a length of 9 inches. Let the length of QR¯ be x inches. It follows that the perimeter of triangle PQR is 9+9+x inches. Since it's given that the perimeter of triangle PQR is 31 inches, it follows that 9+9+x=31, or 18+x=31. Subtracting 18 from both sides of this equation gives x = 13 . Therefore, the length, in inches, of QR¯ is 13 .

Choice A is incorrect and may result from conceptual or calculation errors.

Choice C is incorrect and may result from conceptual or calculation errors.

Choice D is incorrect and may result from conceptual or calculation errors.