## Basic College Mathematics (10th Edition)

Estimate: 22 + 4 = 26 Exact: $26\frac{5}{24}$
$21\frac{7}{8}+4\frac{5}{15}$ First Lets Find Estimate: $21\frac{7}{8}$ rounds to 22 $4\frac{5}{15}$ rounds to 4 Now, $21\frac{7}{8}+4\frac{5}{15}$ = 22 + 4 = 26 Now find Exact: $21\frac{7}{8}+4\frac{5}{15}$ = $\frac{21\times8+7}{8}+\frac{4\times15+5}{15}$ = $\frac{175}{8}+\frac{65}{15}$ = $\frac{175\times15}{8\times15}+\frac{65\times8}{15\times8}$ (LCM of 8 & 15 are 120) = $\frac{2625}{120}+\frac{520}{120}$ = $\frac{3145}{120}$ = $26\frac{25}{120}$ = $26\frac{5}{24}$