Question Bank / Math / Lines, Angles, and Triangles

Lines, angles, and triangles SAT question

Math · Geometry and Trigonometry · Hard · Answer it here, explanation included.

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?

Enter a number or fraction (like 3/17 or 0.176). Press Enter to check.

ExplanationShow

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.

Drill this skill on Aceit

Adaptive practice, a daily plan, and score tracking take a free account so we can save your work.

Practice this skill

More Lines, angles, and triangles questions