Question 257506
the perimeter of a semi-circle is doubled when the radius is increased by 6. Find the radius 

Let R be the radius of the circle. Note that 2*R is equal to the diameter.

Then the perimeter of the semi-cirle is [(2*R)*pi)]/2 = R*pi.

If we increase R by 6 the perimeter is doubled so:

2*(R*pi) = (R+6)*pi

Solve for R.

Use pi = 3.1416.