Adding and Subtracting

Adding 3-digit numbers

Add two numbers up to 999, carrying a ten or a hundred where you need to.

Big numbers are added in columns: ones under ones, tens under tens, hundreds under hundreds. Start at the ones and work leftwards.

When a column is too full

If a column comes to ten or more, only its ones digit stays. The extra ten is carried into the next column along.

Worked example

What is 156 + 127?

  1. Ones: 6 + 7 = 13. Write the 3 and carry one ten.

    Thirteen ones is one ten and three ones.

Try it together

Let us add 348 + 256 together.

Work from the ones leftwards, and carry whenever a column reaches ten.

    1.Ones first. What is 8 + 6?

    Have a go

    Have a go on your own: 417 + 265 = ?

    Hint: The ones make twelve, so a ten is carried.

    Ready to practise?

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

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