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Expanded Fractions and Decimals
Task
Complete the table.
| Fraction | Expanded Fraction Form | Expanded Decimal Form | Decimal |
| $43 \frac{65}{100}$ | $40 + 3 + \frac{6}{10} + \frac{5}{100} $ | $40 + 3 + 0.6 + 0.05$ | $43.65$ |
| $21 \frac{90}{100}$ | |||
| $40 \frac{76}{100}$ | |||
| $7 \frac{82}{100}$ | |||
| $18 \frac{3}{100}$ |
IM Commentary
The purpose of this task is for students to show they understand the connection between fraction and decimal notation by writing the same numbers both ways. Comparing and contrasting the two solutions shown below shows why decimal notation can be confusing. The first solution shows the briefest way to represent each number, and the second solution makes all the zeros explicit.
Solutions
Solution: Supressing unnecessary zeros
| Fraction | Expanded Fraction Form | Expanded Decimal Form | Decimal |
| $43 \frac{65}{100}$ | $40 + 3 + \frac{6}{10} + \frac{5}{100} $ | $40 + 3 + 0.6 + 0.05$ | $43.65$ |
| $21 \frac{90}{100}$ | $20 + 1 + \frac{9}{10} $ | $20 + 1 + 0.9 $ | $21.9$ |
| $40 \frac{76}{100}$ | $40 + \frac{7}{10} + \frac{6}{100} $ | $40 + 0.7 + 0.06$ | $40.76$ |
| $7 \frac{82}{100}$ | $7 + \frac{8}{10} + \frac{2}{100} $ | $7 + 0.8 + 0.02$ | $\hskip 6pt 7.82$ |
| $18 \frac{3}{100}$ | $10 + 8 + \frac{3}{100} $ | $10 + 8 + 0.03$ | $18.03$ |
Solution: Keeping all zeros
| Fraction | Expanded Fraction Form | Expanded Decimal Form | Decimal |
| $43 \frac{65}{100}$ | $40 + 3 + \frac{6}{10} + \frac{5}{100} $ | $40 + 3 + 0.6 + 0.05$ | $43.65$ |
| $21 \frac{90}{100}$ | $20 + 1 + \frac{9}{10} + \frac{0}{100} $ | $20 + 1 + 0.9 + 0.00$ | $21.90$ |
| $40 \frac{76}{100}$ | $40 + 0 + \frac{7}{10} + \frac{6}{100} $ | $40 + 0 + 0.7 + 0.06$ | $40.76$ |
| $7 \frac{82}{100}$ | $\hskip 6pt 0 + 7 + \frac{8}{10} + \frac{2}{100} $ | $\hskip 6pt 0 + 7 + 0.8 + 0.02$ | $\hskip 6pt 7.82$ |
| $18 \frac{3}{100}$ | $10 + 8 + \frac{0}{10} + \frac{3}{100} $ | $10 + 8 + 0.0 + 0.03$ | $18.03$ |
Expanded Fractions and Decimals
Complete the table.
| Fraction | Expanded Fraction Form | Expanded Decimal Form | Decimal |
| $43 \frac{65}{100}$ | $40 + 3 + \frac{6}{10} + \frac{5}{100} $ | $40 + 3 + 0.6 + 0.05$ | $43.65$ |
| $21 \frac{90}{100}$ | |||
| $40 \frac{76}{100}$ | |||
| $7 \frac{82}{100}$ | |||
| $18 \frac{3}{100}$ |
Comments
Log in to commenttsalerno@cox.net says:
about 6 yearsWhat if a student writes the answer to 21 90/100 and 20 + 1 + 9/10 and 20 + 1 + 0.9? This is correct mathematically. Will it get full credit?
Kristin says:
about 6 yearsIf I understand your question, the answer to this is yes (that is how it is shown in the first solution). The idea is that students might do it either way, so two (correct) solution approaches are shown.