# SAT Math Multiple Choice Practice Question 469: Answer and Explanation

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**Question: 469**

**10.**

In Δ*ABC* above, if *AC* = 8, what is the length of ?

A. 8

B. 8

C. 6

D. 4

E. 3

**Correct Answer:** D

**Explanation:**

**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.