A key part of maths in Year 3 is to be confident with working with 3-digit numbers. Before children can really understand a 3-digit number such as 345 they must:

1. be able to count up in tens from zero to 100
2. understand the place value of each digit

Before reading 3-digit numbers it is important that children can confidently count up in tens.

The tens numbers are a strange collection:

ten, twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety

Most of them give a clue that they are tens e.g. sixty suggests 6t or 6 tens

but twenty and thirty do not quite match this pattern.

Understanding place value is the key to understanding number.

In the number 345

the 5 has a value of 5 ones (5)

the 4 has a value of four tens (40)

the 3 has a value of 3 hundreds (300), so the number is:

three hundred and forty-five

It might seem obvious to us, but it is well worth pointing out to children that all numbers, however big or small are made up from just 10 digits: 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9.

The size of the number depends on the place where the digit sits, or place value.

Calculators are a great way to show what happens when you key in a 3-digit number. Try it yourself.

If you want to write 345 on the calculator you start with the 3. At this point, before you key in any other numbers the calculator is showing just 3 ones.

Key in the second part of 345, that is the 4, and see what has happened.

The 4 has gone into the ones, pushing the 3 one place to the left into the tens. The number shown on the calculator is now 34. (Nothing like the number we are trying to type.)

Now key in the 5 and see what has happened.

The 5 has gone into the ones, pushing the 4 one place to the left, into the tens and the 3 from the tens into the hundreds. Only at this point are the digits in the correct place.

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