You want to plot \(\frac{2}{3}\), \(\frac{1}{6}\), \(\frac{3}{4}\), and \(\frac{5}{12}\) on a number line.
a) Why is a \(12\,\text{cm}\) interval from \(0\) to \(1\) more convenient than a \(10\,\text{cm}\) interval?
b) Give another useful length for the interval from \(0\) to \(1\).
c) Order the fractions from least to greatest based on their positions.
Hints
- Find the least common multiple of the denominators.
- Choose a unit length that is easy to divide into twelfths.
- Rewrite all fractions in twelfths before ordering them.
Solution
1. The least common multiple of \(3\), \(6\), \(4\), and \(12\) is \(12\).
2. With a \(12\,\text{cm}\) unit interval, each twelfth is exactly \(1\,\text{cm}\). With a \(10\,\text{cm}\) unit interval, each twelfth is \(\frac{5}{6}\,\text{cm}\), which is harder to mark accurately.
3. Another useful unit length is \(6\,\text{cm}\), because each twelfth is \(\frac{1}{2}\,\text{cm}\). A \(24\,\text{cm}\) interval would also work.
4. Rewrite the fractions in twelfths: \(\frac{1}{6}=\frac{2}{12}\), \(\frac{5}{12}\), \(\frac{2}{3}=\frac{8}{12}\), and \(\frac{3}{4}=\frac{9}{12}\).
5. Therefore, \(\frac{1}{6}<\frac{5}{12}<\frac{2}{3}<\frac{3}{4}\).
Answer
a) A \(12\,\text{cm}\) interval makes each twelfth exactly \(1\,\text{cm}\).
b) One possible length is \(6\,\text{cm}\).
c) \(\frac{1}{6}<\frac{5}{12}<\frac{2}{3}<\frac{3}{4}\)