The formula for the circumference of a circle is:
[tex]C=2\pi r[/tex]
Where r is the radius of the circle.
The radius is given to be 13 and we want to use 3 for π, so:
[tex]\begin{gathered} C\approx2\cdot3\cdot13 \\ C\approx2\cdot39 \\ C\approx78 \end{gathered}[/tex]
