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Geometry and Trigonometry Difficulty: Hard
The figure presents right triangle A B C, where angle C is a right angle. Side A C is horizontal, such that vertex A is to the left of vertex C, and vertex B is directly above vertex C. A vertical line segment is drawn from a point on side A B to a point on side A C and divides side A C into two segments. The length of the segment between vertex A and the vertical line segment is labeled 5 and the length of the segment between the vertical line segment and vertex C is labeled 7. The vertical line segment is labeled x. Side B C is labeled y. A note states the figure is not drawn to scale.

The area of triangle ABC above is at least 48 but no more than 60. If y is an integer, what is one possible value of x ?

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Explanation

The correct answer is either the fraction 10 over 3, the fraction 15 over 4, or the fraction 25 over 6. The area of triangle ABC can be expressed as one half times, open parenthesis, 5 plus 7, close parenthesis, times y or 6 y. It’s given that the area of triangle ABC is at least 48 but no more than 60. It follows that 48 is less than or equal to 6 y, which is less than or equal to 60. Dividing by 6 to isolate y in this compound inequality yields 8 is less than or equal to y, which is less than or equal to 10. Since y is an integer, y equals 8, 9, or 10. In the given figure, the two right triangles shown are similar because they have two pairs of congruent angles: their respective right angles and angle A. Therefore, the following proportion is true: the fraction x over y equals the fraction 5 over 12. Substituting 8 for y in the proportion results in the fraction x over 8 equals the fraction 5 over 12. Cross multiplying and solving for x yields the fraction 10 over 3. Substituting 9 for y in the proportion results in the fraction x over 9 equals the fraction 5 over 12. Cross multiplying and solving for x yields the fraction 15 over 4. Substituting 10 for y in the proportion results in the fraction x over 10 equals the fraction 5 over 12. Cross multiplying and solving for x yields the fraction 25 over 6. Note that 10/3, 15/4, 25/6, 3.333, 3.75, 4.166, and 4.167 are examples of ways to enter a correct answer.