Question 491907
Perimeter of semi-circle is half the circumference.
--> {{{(1/2)*2*pi*r = pi*r}}}
If you double that it equals {{{pi(r+0.5)}}}
--> {{{2*pi*r = pi(r+0.5)}}}
Solve for r
--> {{{2*pi*r = pi*r+0.5pi}}}
-->{{{pi*r = 0.5pi}}}
--> {{{r = 0.5}}}
The radius is 0.5
Another way of looking at it is the perimeter is {{{pi*r}}}, and {{{pi}}} is constant so the only way to double the perimeter is to double the radius
--> 2r = r + 0.5
--> r = 0.5