Make a Ten

A mental-math strategy that makes a lot of two-digit addition fast — no paper, no carrying.

What we're learning

The "make a ten" idea: split one number to get the other to a round ten
How this turns hard addition into easy addition
When this strategy fits and when it doesn't

The trick

Suppose you want to add 8 + 5 in your head.

A child who knows this strategy thinks:

"8 needs 2 more to make 10."
"I'll take 2 from the 5: that leaves 3."
"10 + 3 = 13."

A child who doesn't think:

"8, 9, 10, 11, 12, 13. So 13."

Both reach 13. The first gets there in two steps you can do in your head almost instantly. The second is doing real work that gets slower for bigger numbers.

Why this is THE strategy

For mental two-digit addition, "make a ten" is the single most powerful technique. Once kids have it cold:

28 + 5 → "28 needs 2 more to make 30. Take 2 from 5, leaves 3. 30 + 3 = 33."
47 + 8 → "47 needs 3 more to make 50. Take 3 from 8, leaves 5. 50 + 5 = 55."
65 + 9 → "65 needs 5 more to make 70. Take 5 from 9, leaves 4. 70 + 4 = 74."

It works because round tens are easy to add to. The whole game is getting to the next round ten.

Prerequisites

This strategy only works if your child has:

Bonds to ten. Knows that 8 needs 2 to make 10, 7 needs 3, 6 needs 4, etc. cold. (If not, go back to bonds-to-five and build up.)
Place value comfort. Knows 30 + 3 = 33 instantly, not by counting.

If both are solid, "make a ten" clicks in a week of practice.

Try it together

Round 1: warm up with bonds to ten.

"What goes with 8 to make 10?" "2."
"What goes with 6 to make 10?" "4."
"What goes with 9 to make 10?" "1."

Repeat until they answer in under a second.

Round 2: small make-a-ten problems.

8 + 5
9 + 4
7 + 6
8 + 7
9 + 8

For each one, narrate the strategy out loud the first few times, then ask them to narrate it.

Round 3: 2-digit + 1-digit.

28 + 5
47 + 8
36 + 9
65 + 7

The strategy is exactly the same — get to the next round ten, then add what's left.

When it doesn't fit

Some additions don't have a clean "next ten" jump. 34 + 12 doesn't benefit much — both numbers are far from a round ten, and the column algorithm is faster. That's fine. "Make a ten" is one tool in the toolbox, not the only tool.

A child who knows when to use it AND when to fall back to columns is in good shape.

Watch for

Splitting the wrong number. "47 + 8 → I'll split the 47 into 40 + 7." Then they're stuck. The trick is to split the SMALLER number to bridge the bigger to a round ten. Practice noticing which number is closer to a round ten.
Refusing because it feels harder. First few times, the strategy will feel slower than counting up. That's normal — it's a new mental motion. Push through; speed comes within a week of regular use.

Where this is going

You've finished the K-2 → Grade-1 transition. Two-digit addition is fluent. Next would be: subtraction with regrouping (mirror of this module), then introduction to multiplication via repeated addition. The same place-value foundation everything you've built carries forward.