# SAT Math Multiple Choice Practice Question 528: Answer and Explanation

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**Question: 528**

**6.**

In the figure above, and are radii of the circle with center *A*. If Δ*ABC* has area 18, what is the circumference of the circle?

A. 6π

B. 9π

C. 12π

D. 18π

E. 36π

**Correct Answer:** C

**Explanation:**

**C** Because and are each radii of the circle, you know they are equal in length. This means that the triangle *ABC* must be isosceles, and the base and the height are equal. What base and height would give the triangle an area of 18? The base and height would each have to equal 6, because × 6 × 6 = 18. Because the circumference of the circle is equal to 2π*r*, the circumference will be equal to 12π.