Area of a Circle: Increasing a specific element by addition of.....or multiplication by.......

How will the area of a circle change if its radius is doubled?

It will increase by 4 times.

How will the area of a circle change if we double its diameter?

It will increase by 4 times.

How will the area of the circle change if we increase the radius to 2 cm?

It will increase by$4\pi r+4\pi$

How will the area of the circle change if we increase the diameter to 3 cm?

It will increase by $\frac{6\pi k}{4}+\frac{9\pi}{4}$.