A 2-digit number is just "boxes of ten + loose pieces", so we add and subtract one column at a time, starting with the ones. When loose pieces reach 10, we "bundle a box" and send it up to the tens — that's carrying. When there aren't enough loose pieces to subtract, we "open a box into 10 pieces" — that's borrowing. Once a child sees that carrying and borrowing are really just bundling and opening boxes, the column method on their homework clicks.
Ones 3 + 4 = 7, tens 2 + 1 = 3 → 37 (no carrying)
Ones 7 + 5 = 12, that's 10 — bundle a box, carry 1 → 42
42 − 15: not enough ones, open a box to borrow → 27
💡 For parents
Pairing the game with real objects at home works wonders — rubber bands in bundles of 10, or 10 craft sticks tied together. Have your child say it aloud: "ones first, then tens", and when carrying, "that's ten — bundle a box and send it up"; when borrowing, "not enough — open a box into ten pieces". Play for about 10 minutes, then pick up a pencil and try a real homework problem right away so it sticks.
Start with the picture: a 2-digit number is "boxes of ten + loose pieces". Work one column at a time starting with the ones. This game walks through it step by step with spoken guidance — when loose pieces reach 10, your child bundles a box and sees carrying happen; when subtraction runs short, they open a box and see borrowing happen. That matches the teaching principle of understanding "why" before "how".
Tie them to "bundling" and "opening" a box — carrying is: 10 loose pieces get bundled into 1 box and sent up to the tens; borrowing is: the ones run short, so we open a box from the tens into 10 pieces. When kids watch the blocks move while the column digits change at the same time, they understand where the carried/borrowed number comes from.
Yes — the game shows problems in vertical column form exactly like a homework notebook, and has your child answer one column at a time just like writing it out. Once they're fluent, have them try the next homework problem right away; they'll follow the same steps on their own.
It's free, with no download and no sign-up. Open it in your browser and play with your child right away — on phone, tablet, or computer.