Answer
Estimated answer = 9
Exact answer = $8\frac{2}{15}$
Work Step by Step
$20\frac{3}{5}$ - $12\frac{7}{15}$
Estimation:
$20\frac{3}{5} \approx 21$
$12\frac{7}{15} \approx 12$
Therefore
$20\frac{3}{5}$ - $12\frac{7}{15}$ $\approx$ 21 - 12 = 9
Exact Calculation:
$20\frac{3}{5}$ - $12\frac{7}{15}$
= $20\frac{3\times3}{5\times3}$ - $12\frac{7}{15}$
(15 is the least common denominator)
= $20\frac{9}{15}$ - $12\frac{7}{15}$
= ($20$ - $12$) + ($\frac{9}{15}$ - $\frac{7}{15}$)
(Solving whole parts separately and fractional parts separately)
= $8$ + $\frac{9 - 7}{15}$
= $8$ + $\frac{2}{15}$
= $8\frac{2}{15}$
The estimate was 9, so the exact answer of
$8\frac{2}{15}$ is reasonable.
