Year level: 4

Strand: Number / Measurement

Lesson length: 45–60 mins

In this lesson, students learn about place value and how it extends beyond whole numbers. They use drinking straws to model decimals.

### Achievement standard

Students use their understanding of place value to represent tenths and hundredths in decimal form and to multiply natural numbers by multiples of 10.

### Content descriptions

Students recognise and extend the application of place value to tenths and hundredths and use the conventions of decimal notation to name and represent decimals. AC9M4N01

Students use equivalent representations of fractions using related denominators and make connections between fractions and decimal notation. AC9M4N03

Students interpret unmarked and partial units when measuring and comparing attributes of length, mass, capacity, duration and temperature, using scaled and digital instruments and appropriate units. AC9M4M01

### General capabilities

Numeracy

The following formative assessment is suggested for this lesson.

Exit ticket

Choose any item from the classroom and describe its length in units of a whole drinking straw and decimal.

Enabling prompts: What is the length of your chosen item measured using a drinking straw?

Extending prompts: How can you accurately measure the length of your chosen item using a drinking straw?

Assess students on their use of tenths of a straw or whether they more accurately describe length in hundredths of a straw.

Place value: the value of a digit as determined by its position in a number relative to the ones place. For integers, the ones place is occupied by the rightmost digit in the number before the decimal point.

Base-10: a number system which uses the digits 0–9, and the value of the digit is determined by its face value and its place value, for example, 283 = (2 × 100) + (8 ×  10) + (3 × 1) and 283 = 200 + 80 + 3.

Decimal: used to describe aspects of the base-10 number system. The decimal point separates the whole number part of a number from its decimal part.

• When dividing or multiplying by a multiple of 10, students are often encouraged to ‘hop the dot’ or ‘add a magic zero’. This is unhelpful language for learning. The decimal point never moves and always remains between the ones and tenths. The language of adding a zero confuses students when fractional numbers are involved: for example, 10 x eighteen and a half is not 180.5 or 108.5 it is 185.
• Students often will apply their whole number thinking when reading and interpreting decimal numbers and will assume that decimal numbers with more digits have a higher value, for example, 0.36 is larger than 0.5, just as 36 is larger than 5 this is known as the longer-is-larger misconception.
• Students incorrectly read decimals, again applying their whole number thinking, for example, 0.36 is read as zero point thirty-six, instead of stating that we white zero point three six and read it as thirty-six hundredths.

## What you need:

• Lesson plan (Word)

• Same and different slides (PowerPoint)

• Place value chart slides (PowerPoint)

• Drinking straws and scissors

• Sheet of paper, pencils, markers