Circumference $= π$ (diameter)
Area $=$ (radius)^{$^{2}$} $π$

What measurement is given in the diagram?

To find the circumference, substitute the diameter into the equation.To find the area, you must find the radius from the diameter.

Remember that the diameter is $2$ times the radius.

$C = π (15)$
$A = (7.5)^2π$

$A = 176.7$ m^{$^{2}$}
$C = 47.1$ m

See part (a).

In this equation, you are given the circumference. With this, you must find the radius in order to find the area.

Since Circumference $= 2$ (radius)$π$
$\text{Radius }=\frac{\text{Circumference}}{2\pi}$

Radius $= 50$ cm
Area $=$ (radius)^{$^{2}$}$π$

Area $= 7853$ cm^{$^{2}$}