Adding and Subtracting

Making and breaking tens

Swap ten ones for one ten, and break one ten back into ten ones.

Ten ones and one ten are worth exactly the same. Swapping one for the other is what makes big adding and taking away work.

Have a play

Thirty ones in a row, with a number written at every fifth mark. Move along the line and see where the tens fall.

Tap anywhere on the line.

Worked example

What is 28 + 5?

  1. The ones first: 8 + 5 = 13.

    That is more than ten, so a swap is coming.

Try it together

Now the other way: 42 − 7.

    1.You cannot take 7 from 2 ones. Break one ten open. How many ones does that give you?

    Watch out

    Breaking a ten does not lose anything. 42 is 4 tens and 2 ones, and it is also 3 tens and 12 ones.

    Have a go

    Have a go: 36 + 8

    Hint: Start with 6 + 8 and see if a new ten appears.

    Ready to practise?

    Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.

    Print a worksheet