When children work out 8 + 5, something new happens: the answer goes past a ten. Many children then count five steps on their fingers and lose track at ten. That is not strange. Bridging through ten is one of the first places where numbers really start to connect, and it is part of the core content of the Swedish national curriculum (Lgr22) for Years 1–3 (mental arithmetic methods and the four operations).
What your child really needs to know first
Before 8 + 5 feels easy, your child needs to know the number bonds to 10: 8 and 2, 7 and 3, 6 and 4, and so on. Then they can split 5 into 2 and 3, do 8 + 2 = 10 and then add 3. That is the whole trick, and you can practise it without a pencil. If the number bonds are not secure yet, that is where to start, not with 28 + 5.
Use the school's models
Ask the teacher, or look in your child's book, which models the class uses: often a grid of ten squares (a ten frame) and a number line. Use the same models at home. Then your child does not have to keep track of two different methods, and research on learning maths suggests that a small number of recurring models helps when the tasks become more abstract.
- Draw a number line on a long piece of paper, or with tape on the hall floor. Hop 8 + 5 by hopping to 10 first and then 3 more.
- Fill a ten frame with eight buttons. Add five more, and ask how many fit before the frame is full.
- Put out 13 buttons and split them: take away 3 so that there are 10, then take away 3 more. That is how 13 − 6 works.
Ask how your child worked it out
The most useful thing you can say is “how did you work it out?”. A child who says “8 and 2 is 10, then 3 more” has understood bridging through ten, even if the answer comes out wrong through a slip. A child who only gives the right answer may have guessed or counted on their fingers. If you praise what your child did (“you split the five, clever”), you strengthen the strategy, not just the answer.
Common pitfalls
- Your child counts every step on their fingers and loses track at ten.
- Your child forgets that the tens change: 28 + 5 becomes 23, or 31 − 7 becomes 36.
- Your child mixes up 13 and 31.
- With subtraction, your child takes away in the wrong direction at the ten.
All of these pitfalls are normal and can be practised away. Notice which one you see and practise just that for a little while.
Short and often beats long and rarely
Research on spaced repetition shows that many short moments stick better than one long one. Ten minutes on four or five days a week is plenty. A card game is an easy way in: draw two cards and add them up, and see if you can find number bonds to 10. You can also use an ordinary pack of cards to practise place value, where two cards make a number of tens and ones.
If it is hard going
If it ends in tears, take a break. Nobody learns anything when things boil over. Come back the next day with a smaller piece, for example just the number bonds to 10. If it is often hard going for several weeks, it is a good idea to write a few lines to the teacher about where it got stuck. Then the school can adapt the teaching. You do not need a diagnosis to ask for support.
If you want to practise with an app
In Lärkompis, bridging through ten is two skills of its own, “Plus över tio” (adding across ten) and “Minus över tio” (subtracting across ten), with five levels each. Level 1 is, for example, 7 + 4 with the ten frame visible, and level 5 is a two-digit number plus a one-digit number across the ten in a word problem. The correct answers always come from code, not from a language model. See the full list for maths in Year 2 to find out what else is practised at the same time.
