# SAT Math Multiple Choice Practice Question 103: Answer and Explanation

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**Question: 103**

**15.**

Given that ACBD is a square, its area is

A. 12

B. 36

C. 72

D. 144

E. 288

**Correct Answer:** C

**Explanation:**

C. This question is a tricky case of the 45-45-90 triangle. The 12 on the triangle's base is actually its hypotenuse, and the helpful formula list at the start of each math section tells you that the hypotenuse of this special type of triangle is , where x is the length of a leg. That means each leg must be , which is just an annoying number. But no fear! The leg of the triangle is also the side of the square, which means that the square's area is

.