SAT Math Multiple Choice Practice Question 469: Answer and Explanation

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Question: 469


In ΔABC above, if AC = 8, what is the length of ?

A. 8
B. 8
C. 6
D. 4
E. 3

Correct Answer: D


D The sides of a 45°-45°-90° triangle have a special pattern, which you can find in the gray box at the beginning of every Math section. Each leg of a 45°-45°-90° triangle is equal to the hypotenuse divided by . Because the hypotenuse in triangle ABC is 8, must be equal to . You can't have a square root on the bottom of a fraction; so multiply the top and the bottom by . That gives you . Meanwhile, you can use Ballparking to eliminate A and B. Because the hypotenuse of a right triangle is always the longest of the three sides, must be less than 8.

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