The key target in Year 3 is for children to recognise the place value of each digit in **3-digit numbers**. They should know that 10 tens are equivalent to 1 hundred and that 100 is ten times the size of 10 and be able to work out how many 10s there are in any 3-digit multiple of 10.
As the numbers get larger it is harder to find practical examples for children to work with but they should have practice with making a unit of 1 hundred out of 10 units of 10, for example using cubes joined in blocks of ten or straws bundled into tens.
Terms such as, ‘multiples of 10’ are frequently used but it is important that children can explain that numbers such as 170 and 450 are multiples of 10 because they are each equal to a whole number of tens and that this can be recognised by there being a zero in the ones place. It might seem obvious but by talking and asking questions it can become clear whether children have grasped this.
Watch out for a common mistake that children make when writing a 3-digit number such as one hundred and four; written as 1004.