Question 1061322
I take increasing something by 200% to mean x + 2x = 3x

So if you triple the diameter, the circumference will triple because there is a linear relationship {{{ C =pi*D}}}   (More often you see {{{ C=2(pi)r }}} but {{{ D=2r }}}  so either way of writing it is valid).

Or, I guess you can say you also increase the circumference by 200% :-)