If the diameter of a circle changes from 6 cm to 12 cm, how will the circumference change? A) multiplies by 1 2 B) multiplies by 2 C) increases by 6 D) decreases by 6

The formula for the circumference of a circle is 2*r*pi, where r is radius, and r=d/2.

If d = 6cm, then r = d/2 = 3 cm, and the circumference is 2*r*pi = 6*pi

If d = 12cm, then r = d/2 = 6 cm, and the circumference is 2*r*pi = 12*pi

12*pi/6*pi = 2

The circumference will be B) multiplied by 2.