Mystery decimals
This is a level 4 number activity from the Figure It Out series. It is focused on converting between fractions and decimals. A PDF of the student activity is included.
About this resource
Figure It Out is a series of 80 books published between 1999 and 2009 to support teaching and learning in New Zealand classrooms.
This resource provides the teachers’ notes and answers for one activity from the Figure It Out series. A printable PDF of the student activity can be downloaded from the materials that come with this resource.
Specific learning outcomes:
- Convert between fractions and decimals.
Mystery decimals
Achievement objectives
NA4-5: Know the equivalent decimal and percentage forms for everyday fractions.
Required materials
- Figure It Out, Levels 3–4, Basic Facts, "Mystery decimals", page 21
- calculator (optional)
See Materials that come with this resource to download:
- Mystery decimals activity (.pdf)
Activity
This activity gives students practice at relating common fractions to decimals and vice versa. Students at this level should have experienced writing tenths and hundredths as a decimal and writing a decimal for any fraction expressed in tenths and hundredths. This will not necessarily mean that they can express other fractions as decimals.
Some sense of the relative size of fractions will be helpful in these situations, such as knowing that 3/5 is a little more than half or that 2/8 is the same as 1/4. Some examples are easily changed to a decimal, for example, 4/5 = 8/10, which is equal to 0.8.
Alternatively, the students should think of a fraction as a division equation, for example, 4/5 means 4 ÷ 5 or
When the students are making up their own problems, you may want to limit the denominators that they use. They could use calculators to explore possibilities for creating equations.
As a variation, the students could use the inequation symbols > < in these statements, or you could give them some examples for which they have to supply the correct operator, < or >. For example, 3/4 ? 5/8, 2/3 ? 3/5, and so on.
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Answers will vary.
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