What happens to the circumference of a circle if you double the radius?

Let original area = (pi)r^2

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If you couble the radius, area = (pi)(2r)^2 = 4(pi)r^2

What happens if you double the diameter? it would double also.

 What happens if you triple the radius? If you triple the radius of a circle . . .

-- You should not expect anything to happen. Those around are likely to remain

completely unaware that you have done anything to your circle. 

-- You wind up with a circle that's three times as big as it used to be. 

-- The diameter of the circle is three times the original diameter. 

-- The circumference of the circle is three times the original circumference. 

-- The area of the circle is nine times the original area.