If a child knows instantly that 6 and 4 make 10, a great deal of later arithmetic becomes easier. If they do not, almost everything stays slow. Combinations of 10 are the single highest-leverage thing to work on in early elementary math, and they are worth more classroom time than they usually get.
Why they carry so much weight
Adding 8 + 5 is hard if you count. It is easy if you know that 8 needs 2 more to make 10, leaving 3 — so the answer is 13. That move, called Making 10, is the backbone of addition within 20, and it is unavailable to a child who does not know the pairs cold.
The same knowledge carries into subtraction as missing addends, into place value and the teen numbers, and eventually into mental strategies for much larger numbers. Time spent here pays back for years.
Start with the quantity, not the equation
Children need to see 10 as a structure before they manipulate it as a symbol. A ten frame does this well: five in a row, then five more, so 7 is visibly 5 and 2, and visibly 3 short of full.
- Game 1 Sleeping Bears — hide some bears, arrange the rest on a frame, and work out how many are hidden. The frame does the explaining
- Game 7 Sleeping Bears — the same game with all ten bears and a recording sheet, so each combination gets written down
Then make them retrieve it, repeatedly
Once the structure is there, children need volume — many retrievals, in a setting where being slow is mildly inconvenient rather than shameful.
- Game 8 Go Fish for 10s — you cannot take a turn without computing a missing addend, so every question is a rep
- Game 9 Erase — spot every pair making 10 among seven dice, where spotting more lowers your score
- Game 10 Square Deal — add a single digit to 10 and say the equation out loud
Then apply it to bigger numbers
The point of knowing the pairs is using them. These push children to apply the combinations rather than just recall them.
- Game 23 Dirty Dozen — find the distance from your roll to 10, every single turn
- Game 24 First to 20 — hit 20 exactly, which means constantly tracking how far away you are
What to watch for
The signal that this has landed is not speed on a timed test. It is a child reaching for Making 10 unprompted when they meet 8 + 5 — pulling 2 across without being told to. Until that happens, more practice on the pairs is time well spent.
All of these games are in the Addition/Subtraction collection, or together as the Addition/Subtraction Bundled Game.