## Basic College Mathematics (10th Edition)

Estimated answer = 10 Exact answer = $10\frac{3}{8}$
$17$ - $6\frac{5}{8}$ = $16\frac{8}{8}$ - $6\frac{5}{8}$ Estimation: $6\frac{5}{8} \approx 7$ Therefore $17$ - $6\frac{5}{8}$ $\approx$ 17 - 7 = 10 Exact Calculation: $16\frac{8}{8}$ - $6\frac{5}{8}$ = $16$ + $\frac{8}{8}$ - ($6$ + $\frac{5}{8})$ = $16$ + $\frac{8}{8}$ - $6$ - $\frac{5}{8}$ = ($16$ - $6$) + ($\frac{8}{8}$ - $\frac{5}{8}$) (Solving whole parts separately and fractional parts separately) = $10$ + $\frac{8 - 5}{8}$ = $10$ + $\frac{3}{8}$ = $10\frac{3}{8}$ The estimate was 10, so the exact answer of $10\frac{3}{8}$ is reasonable.