Question in-tri
In triangle , angle is a right angle, point lies on , point lies on , and is parallel to . If the length of is units, the length of is units, and the area of triangle is square units, what is the length of , in units?
In triangle R S T , angle T is a right angle, point L lies on
Hard-difficulty · SAT Math · Lines, Angles, and Triangles — Angle relationships (parallel lines). Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.
Answer explanation
The correct answer is . It's given that in triangle , angle is a right angle. The area of a right triangle can be found using the formula , where represents the area of the right triangle, represents the length of one leg of the triangle, and represents the length of the other leg of the triangle. In triangle , the two legs are and . Therefore, if the length of is and the area of triangle is , then , or . Dividing both sides of this equation by yields . Therefore, the length of is . It's also given that point lies on , point lies on , and is parallel to . It follows that angle is a right angle. Since triangles and share angle and have right angles and , respectively, triangles and are similar triangles. Therefore, the ratio of the length of to the length of is equal to the ratio of the length of to the length of . If the length of is and the length of is , it follows that the ratio of the length of to the length of is , or , so the ratio of the length of to the length of is . Therefore, . Multiplying both sides of this equation by yields . Dividing both sides of this equation by yields . Since the length of , , is the sum of the length of , , and the length of , it follows that the length of is , or . Note that 44/3, 14.66, and 14.67 are examples of ways to enter a correct answer.
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