## Basic College Mathematics (10th Edition)

Estimated answer = 16 Exact answer = $15\frac{7}{8}$
$10\frac{1}{4}$ + $5\frac{5}{8}$ Estimate Calculation: $10\frac{1}{4} \approx 10$ $5\frac{5}{8} \approx 6$ Therefore $10\frac{1}{4}$ + $5\frac{5}{8}$ $\approx$ 10 + 6 = 16 Exact Calculation: $10\frac{1}{4}$ + $5\frac{5}{8}$ = $10\frac{1\times2}{4\times2}$ + $5\frac{5}{8}$ (8 is the least common denominator) = $10\frac{2}{8}$ + $5\frac{5}{8}$ = $10$ + $5$ + $\frac{2}{8}$ + $\frac{5}{8}$ (adding whole part separately and fractional part separately) = $15$ + $\frac{2 + 5}{8}$ = $15$ + $\frac{7}{8}$ = $15\frac{7}{8}$ The estimate was 16, so the exact answer of $15\frac{7}{8}$ is reasonable.