Answer
$8 \text{ dogs}$
Work Step by Step
Using $C=2\pi r$ or the forumula for the circumference, with $C=78.5$ and $\pi=3.14,$ then the radius of the pen is
\begin{array}{l}\require{cancel}
C=2\pi r
\\
78.5=2(3.14) r
\\
78.5=6.28r
\\
\dfrac{78.5}{6.28}=r
\\
r=12.5
.\end{array}
Using $A=\pi r^2$ or the formula for the area of a circle, with $r=12.5,$ then the area of the pen is
\begin{array}{l}\require{cancel}
A=\pi r^2
\\
A=3.14(12.5)^2
\\
A=490.625
.\end{array}
If each dog needs at least $60$ square feet, then the number of dogs that can fit in the pen is
\begin{array}{l}\require{cancel}
\dfrac{490.625}{60}
\\=
8.1770833333333333333333333333333
.\end{array}
Hence, $
8 \text{ dogs}
$ can fit in the pen.
