Adding across ten: how to make 8 + 7 feel easy

What does “adding across ten” mean?

Adding across ten, often called bridging through ten, describes sums where the answer crosses ten, such as 8 + 5 = 13, or where a subtraction drops back below it, such as 13 − 5 = 8. Children usually meet it in the first grade, with numbers up to 20. It is the first step where calculating means more than counting on, and it is the foundation for everything that follows with numbers up to 100.

Many children use their fingers at first. That is completely normal and not a sign of a problem. The goal is that, over time, they build a strategy that is faster and more reliable than counting.

The core idea: make a ten first, then add the rest

For 8 + 5, two more are needed to make ten. So 5 is split into 2 and 3. First 8 + 2 = 10, then 10 + 3 = 13. Subtraction works the other way round: for 13 − 5, go back 3 to reach ten, then 2 more, so 10 − 2 = 8.

It sounds like many steps, but it quickly becomes a habit once the building blocks are secure.

Step 1: know the number bonds to ten

Without number bonds to ten, nothing works. These are all the pairs that make 10: 1 and 9, 2 and 8, 3 and 7, 4 and 6, 5 and 5. Practise them first, in both directions: “I have 6, how many more to make 10?” A card game works well: two players each turn over a card, and whoever says the partner number first keeps the pair.

Step 2: make it visible with material

A twenty frame (two ten frames stacked) has two rows of ten squares. Place 8 counters in the top row and ask: “How many more fill the row?” Then place the remaining counters in the second row. Your child sees that two counters fill the frame and three are left over. Doing becomes understanding. An egg box with ten cups, coins or building bricks work just as well.

Step 3: say the steps out loud

Ask your child to say what they are doing: “I need 2 to make ten, so 3 are left.” Speaking makes the strategy concrete and shows you where it slips. Write the steps down at the beginning; later, saying them is enough.

Step 4: carry the idea to bigger numbers

Once 8 + 7 is secure, try 18 + 7 and 28 + 7. Ask: “What do you notice?” Children see that the same idea keeps working. This transfer is the real success and prepares calculating with numbers up to 100.

Common stumbling blocks

• Miscounting by one. Counting in ones makes off-by-one errors easy. That is a sign to keep working with material and splitting.
• Splitting the wrong way. 8 + 5 becomes 8 + 3 + 2 because the 5 was split incorrectly. A look at the frame helps.
• Subtraction is harder. That is normal. Practise it later and with inverse sums: if 8 + 5 = 13, what is 13 − 5?
• Frustration after many sums. Keep to a few sums and stop while it is still going well.

If your child does not progress after a longer time of calm, regular practice, talk to their teacher. They know how things look in class and can advise specifically.

A three-day practice plan

Day 1: number bonds to ten with cards or a twenty frame, about five minutes. Day 2: make ten: 7 + ? = 10, 9 + ? = 10, then six to eight sums like 9 + 4. Day 3: a small mix of bonds, adding across ten and one or two subtractions.

Stay at ten minutes. After that, a break is better than one more round.

Where Recheneule can help

Recheneule offers grade 1 tasks with numbers up to 20 in short game rounds, with no ads and no account. The app does not replace talking through the method, but it suits quick revision in between. More on the Recheneule page.