# SAT Math Multiple Choice Practice Question 518: Answer and Explanation

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**Question: 518**

**17.** ABCD is a quadrilateral such that *AB* = *BC*, *AD* = *CD* and *AD* = *AB*. If *BC* = 12, what is the perimeter of ABCD?

A. 44

B. 42

C. 40

D. 36

E. 33

**Correct Answer:** E

**Explanation:**

**E** Don't assume that the figure *ABCD* must be a rectangle; it doesn't have to be. All you need to do here is follow the rules: You know that *AB* = *BC* and that *BC* = 12, so you now know two of the four sides (sides *AB* and *BC*) are equal to 12. You know that *AD* is going to be one quarter of *AB*, so *AD* must be equal to 3. Finally, you know that *AD* is one half of *CD*, so *CD* must be equal to 6. This makes the total perimeter 12 + 12 + 3 + 6, or 33.