Tip
The circumference (C) is the distance around a circle. To calculate the circumference (C) of a circle, you need to know either the radius (r) or the diameter (d) of the circle. The radius (r) of a circle is a line segment with one endpoint at the center of the circle and the other endpoint on the circle. The diameter (d) of a circle is a line segment that passes through the center of the circle and has endpoints on the circle. The radius (r), diameter (d), and circumference (C) of a circle are all related by the formulas: d = 2r, C = 2πr, C = πd, where π ≈ 3.14 units.
Sample Problem
The figure shown represents the wheel on a model with center S. If the wheel has made 5 complete revolutions, and RT = 11cm, then, of the following, which is the best estimate for the distance traveled by the wheel?
Answer Options
(A) 55 cm
(B) 110 cm
(C) 165 cm
(D) 220 cm
(E) 330 cm
View Correct Answer
(C) 165
C = πd ≈ 3 × 11 = 33 cm
So 5 revolutions is 5 × 33 = 165 cm.
