If the radius of a circle is tripled what happens to the circumference?

Circumference = pi x diameter so if the radius is 5 then the diameter is 10

Circumference = pi x 10 = 31.415

If we triple the radius to 15, then the diameter is 30, so

Circumference = pi x 30 = 94.245

Which looks like triple the first circumference. So if the radius is tripled, the circumference is also tripled.