Question #N900
A circle has a radius of 5 units. A chord of the circle is 8 units long. What is the distance, in units, from the center of the circle to the chord?
A. 1
B. 2
C. 3
D. 4
Correct Answer is: C
Draw a diagram of the circle with the chord and the radius. Draw a perpendicular segment from the center of the circle to the chord. This perpendicular segment bisects the chord, forming two right triangles. The hypotenuse of each right triangle is a radius of the circle (5 units), and one leg is half the length of the chord (4 units). Using the Pythagorean Theorem, the other leg (the distance from the center of the circle to the chord) is $\sqrt{5^2 - 4^2} = \sqrt{9} = 3$ units.