ANSWER
• r = 5/π in
,• D = 10/π in
,• A = 25/π in²
EXPLANATION
The circumference of a circle is:
[tex]C=2\pi r[/tex]So if we know that the circumference is 10 inches we can find the radius:
[tex]\begin{gathered} 10=2\pi\cdot r \\ r=\frac{10}{2\pi}=\frac{5}{\pi} \end{gathered}[/tex]The diameter is twice the radius:
[tex]D=2r=2\cdot\frac{5}{\pi}=\frac{10}{\pi}in[/tex]And the area of a circle is:
[tex]A=\pi r^2=\pi\cdot(\frac{5}{\pi})^2=\pi\cdot\frac{25}{\pi^2}=\frac{25}{\pi}in^2[/tex]