Answer:
The circumference is tripled
Explanation:
The formula for the circumference is 2πr. If you triple the radius the formula would be 2π3r. the ratio between the two is 2π3r / 2π1r. 2π & r cancels out and you have 3/1 left. Therefore the answer is the circumference is tripled.
The fact that there is no exponential in the formula indicates that the proportional increase is lineal.