A full row is easy to recognise
Imagine a tray with ten spaces. Eight spaces are occupied and you want to add five more counters. Two of those five will fill the tray. That leaves three counters outside it.
You can now see the answer as one full ten and three more: 13. Nothing was added twice. You simply split the five into two and three, using the two where it helped most.
Try it yourself
Draw ten empty spaces and fill nine. You want to add four counters: one fills the empty space, leaving three beside the full ten. Now try the same idea with seven filled spaces and six more counters.
For 9 + 4, one of the four completes the ten and three remain. For 7 + 6, three complete the ten and three remain. Both become 10 + 3. The route changes, but the total stays thirteen.
Know the missing partner
The small pairs that make ten are useful: 1 and 9, 2 and 8, 3 and 7, 4 and 6, and 5 and 5. You can discover them by filling the frame rather than memorising a list immediately.
If you start with six counters, ask “how many empty spaces?” Four empty spaces tell you six needs four to reach ten. If you add only two, you will not fill the tray; the total is eight, and there is no reason to force a ten.
When does making ten help?
Making ten is one strategy, not a rule that every addition must use. With 3 + 2, counting on twice may be simpler. With 8 + 5, the full tray makes the amount easier to keep track of.
Once that exchange feels natural, try the next lesson’s rounding method. It uses a related idea, but temporarily adjusts a number and then corrects for the adjustment.