Question

1.

Answer 1

If the diameter is 12 inches, the radius is 6 inches, because the radius is half the diameter.

Given the formula

$A=\pi r^2$

we have

$A=36\pi$

When you fold the circle in half, the resulting figure has half the area.

So, you start with a circle with area $36\pi$

You fold it once and you have a semicircle with area $18\pi$

You fold it twice and you have a quarter circle with area $9\pi$