Making Ten Strategy

Arithmetic · Axiom Academy

Regroup to a ten first — the central technique of mental addition. Adding to 10 is immediate — the second addend simply becomes the ones digit. So to add two other numbers, first regroup them to form a ten . Watch 8 + 5 : slide 2 dots from the 5 to fill the ten frame, and 8 + 5 becomes the easy sum 10 + 3. Split the 5 so part of it completes the ten 2. The Same Move on a Number Line The regrouping is one jump split into two. Starting at 8 , instead of hopping 5 all at once, jump 2 to land exactly on 10 , then jump the remaining 3 . The landing spot is the answer — and the first jump always aims for the nearest ten. Begin at 8 so the jump to ten is short — only 2. 8 needs 2 to make 10, so the first hop is +2 onto the ten. The 5 splits as 2 + 3: the 2 got used up reaching ten, leaving 3. From 10, hop the remaining 3 to land on 13. Splitting 5 into 2 + 3 is the whole trick: the 2 lifts 8 up to a round ten, and 10 + 3 is a sum you already know by sight. Every make-ten regrouping leans on a pair of numbers that sum to 10. There are only five to know — memorize these and the strategy becomes automatic. These five pairs are worth memorizing — every make-ten regrouping uses one of them. 4. Three Sums, Worked the Make-Ten Way Run the same three steps each time: find what the larger number needs to reach 10 , take that from the smaller number, then add 10 to what's left. 9 needs 1 to make 10. Take that from 4, leaving 3 . 7 needs 3 to make 10. Take that from 6, leaving 3 .

This is the written version of the interactive lesson above. See the full Arithmetic course.