The key idea of number knowledge at level 2 is that our number system is based on groupings of the number ten.
At level 2 students are developing an understanding of place value. Our number system is a place value number system based on the number 10 (the decimal system). We have 10 digit symbols, 0-9, with their value defined by their position within a number. This is frequently represented by the use of place value ‘houses’ with columns to represent the places.
Digits in any column are worth ten times as much as those in the column to its right, for example a 7 in the tens columns represents 7 tens, or 70, while a 7 in the ones column is worth 7 ones, or 7. An understanding of the decimal system and how to use place value is an important part of all further number understanding.
This key idea develops from the key idea of number knowledge at level 1 where students understood that objects in a set can be counted.
This key idea is extended in the key idea of number knowledge at level 3 by an extension from whole numbers into other types of numbers such as fractions, decimals and percentages.