I have some Year 2 students who are working well past the Year 2 Australian Curriculum Achievement Standards for Place Value. These are students who are confident with working with numbers into the millions. As a result, I decided to extend them by teaching them about decimals. It helped that they possessed a solid understanding of fractions, so I could connect this to decimals.
Firstly, I used a pro forma from Nelson Maths to connect fractions to decimals:
We spoke about what each square represented. I asked ‘What is one of these squares called?’ Students answered ‘One tenth’. We then spoke about how the line in fractions (eg 1/10) means divided and when we put a fraction into the calculator we get another number. Students put 1/10 into the calculator and got 0.1. They did this for 2/10, 3/10 and so on and each time they shaded this on the pro forma writing 1/10 and 0.1 beside each shading. They began to understand that decimals were another name for fractions. However, one student whose understanding was not as solid as the others, recorded in his book 0.3 is 1/3 and 0.4 is 1/4 besides his shading.
In the following session, these students modelled decimals using place value mats that had tens, ones and tenths. We used straws to represent the tens and ones. We used a rolled up piece of play dough (the same length as a straw) cut into tenths to represent the tenths. My students chose a decimal to make and they wrote both the decimal and fraction name underneath their model. They took photos on iPads to show me their work, which looked like this:
I found these Nelson Maths based activities to be really helpful when introducing decimals and my students all felt comfortable modelling and describing the decimals they made by the end of the numeracy sessions. It was also valuable to connect the known (fractions) to the unknown (decimals) when teaching decimals.
How have you taught decimals in the classroom? What issues have you faced when teaching decimals?