Hello,

the circumference of circle N is calculated by

Now the radius of circle P is:

Now plug in this term into the formula to calculate the circumference:

That means the circumference of circle P is half as long as the circumference of circle N.

EDIT:

Thus r = 75.36 / 2 = 37.68.

The area of a circle is calculated by:

Plug in the value for r into this formula and you'll get: