# Math Multiple Choice

In the figure above, *AD* is a diameter of the circle
with center *O* and *AO* = 5. What is the length of
arc *BCD* ?

- (A)
- (B)
- (C)
- (D) CORRECT ANSWER
- (E)

##### Explanation:

To solve this problem, it is helpful to draw segment *OB* in the figure. Since *OB* and *OD* are both radii of
the circle, they both equal 5. Therefore, the angles opposite these congruent sides of

*BOD* are congruent
and *OBD* = 36°. The third angle of the triangle, *BOD*, equals

180°- 36°- 36° = 108°. Arc *BCD* is a fraction of the circumference of the circle and more specifically equals , which equals The correct answer is choice (D).