Earth is composed of four main layers, starting with an inner core at the planet's center, enveloped by the outer core, mantle, and crust. The inner core is a solid sphere made of iron and nickel metals about 759 miles (1,221 kilometers) in radius.
source: nasa
The circle with diameter of 24 means that 2

r = 24.
Solving for r, we get

r=24.
Dividing both sides by

, we get r=24/

.
The area of the full circle is

times 24 squared over

. The

being multiplied cancels out, meaning that 24 squared over

is the area of the full circle. 24 squared is 576, and dividing by 16 we get

as the answer.