Chapter 1 - Tools of Geometry - 1-8 Perimeter, Circumference, and Area - Practice and Problem-Solving Exercises - Page 67: 58

$\frac{25n^2}{4}\ units^2$

Use the formula for perimeter to find the length of the side: $P=4s$ $10n=4s$ $10n\div4=4s\div4$ $\frac{10n}{4}=s$ $\frac{(/\!\!2)(5)n}{(/\!\!2)(2)}=s$ $\frac{5n}{2}=s$ Use the formula for the area: $A=s^2$ $A=(\frac{5n}{2})^2$ $A=\frac{25n}{4}^2$