# Place Value Practice (Tenths) Teacherâ€™s Notes

Number, level 3

### Prior knowledge. Students should be able to:

• Write a whole number in expanded form
• Explain the role of the decimal point as separator of the wholes and the parts of a whole
• Explain what tenths are, and write them as both a fraction and a decimal (1/10 = 0.1)
• Model an improper fraction and a mixed number with materials

### During these activities, students will meet:

• Writing a decimal in expanded form, and vice versa
• Place value in decimals
• Convert improper fractions involving tenths to both a mixed number and a decimal
• Adding and subtracting a tenth from a number
• Reading a number line marked in tenths

### Background

With this exercise it can be worthwhile to discuss different ways of shading the same amount.

Exercise 10
This exercise taps into the measure construct of decimals, so may be harder for students to work with than the numbers alone. Questions one and two have each (major) mark standing for a unit, with the little marks being a tenth, which many students should work with easily. However, number three does not conform to this pattern. Do not be surprised if a number of students assume that each (major) mark still stands for one, with each of the little marks being a tenth, and do not realise that they need to start out (when working on any number line) by identifying the scale on the interval. This error is not necessarily one caused by changing the pattern in the questions, for a number of students it is a fundamental misunderstanding of scales.