Informal investigation of teen numbers as 10 and … is introduced in Place Value 4.
Formal place value of teen numbers is introduced in Place Value 7, focusing on Seeing 10 in 2 ways, Teen means 10, What is a digit?, Standard place value of teen numbers using fingers, Standard place value of teen numbers using a 10 frame and Standard place value of teen numbers using the place value chart.
Children now begin to investigate standard and non-standard place value of teen numbers, then twenties numbers, and then higher two-digit numbers.
Children also investigate partitioning two-digit numbers, explaining when the partitions are place values and when they are not.
Children also investigate ordering tens and two-digit numbers on a number line.
Children also investigate finding the nearest 10s number to a two-digit number.
This will allow children to begin to develop the understanding that they will apply to adding and subtracting single-digit numbers bridging 10, 20 and any decade – integrated with Addition and Subtraction 6, Addition and Subtraction 7  Addition and Subtraction 8 and  Addition and Subtraction 9.
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