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Geometry and Trigonometry Difficulty: Hard
The figure presents right triangle M N P. Side M P is horizontal, with vertex M to the left of vertex P. Vertex N lies above side M P, and angle N is a right angle. Point Q lies on horizontal side M P directly below vertex N. Vertical line segment N Q is drawn, forming right triangles M N Q and Q N P. Side M N is labeled 3 and side N P is labeled 4.

In the figure above, what is the length of line segment NQ ?

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Explanation

Choice C is correct. First, line segment M P is the hypotenuse of right triangle M N P, whose legs have lengths 3 and 4. Therefore, open parenthesis, the length of line segment M P, close parenthesis, squared, equals, 3 squared plus 4 squared, so open parenthesis, the length of line segment M P, close parenthesis, squared, equals 25 and the length of line segment M P equals 5. Second, because angle M N P corresponds to angle N Q P and because angle M P N corresponds to angle N P Q, triangle M N P is similar to triangle N Q P. The ratio of corresponding sides of similar triangles is constant, so the length of line segment N Q over the length of line segment M N equals the length of line segment N P over the length of line segment M P. Since M P equals 5 and it’s given that the length of line segment M N equals 3 and the length of line segment N P equals 4, the length of line segment N Q, over 3, equals 4 over 5. Solving for NQ results in the length of line segment N Q equals 12 over 5, or 2.4.

Choices A, B, and D are incorrect and may result from setting up incorrect ratios.