## Basic College Mathematics (9th Edition)

Estimate: $105$ feet Exact: $104\frac{5}{8}$ feet
We know that the perimeter is given by: $Perimeter=side_1+side_2+side_3+side_4$ Thus: $side_4=Perimeter-side_1-side_2-side_3$ We plug in the given values: $side_4=518\frac{3}{4}-108\frac{1}{4}-162\frac{3}{8}-143\frac{1}{2}$ First, we estimate by rounding: $side_4=519-108-162-144=105$ feet Next, we get the exact answer: $side_4=518\frac{3}{4}-108\frac{1}{4}-162\frac{3}{8}-143\frac{1}{2}$ $side_4=518\frac{6}{8}-108\frac{2}{8}-162\frac{3}{8}-143\frac{4}{8}$ $side_4=(518-108-162-143)+(\frac{6}{8}-\frac{2}{8}-\frac{3}{8}-\frac{4}{8})$ $side_4=(105)-\frac{3}{8}$ $side_4=104+\frac{8}{8}-\frac{3}{8}$ $side_4=104\frac{5}{8}$ feet