The tiles · Grades 1 to 5
Carry
Column addition and subtraction with regrouping
On the way This tile's page is up; the playable version follows.
What your child does
Two numbers stacked, worked right to left, one column at a time. Before each column is settled your child commits what it will come to, and the board shows whether a ten was made. The carry is the whole lesson; a column that adds under ten teaches nothing, so the ladder is built around when and where the regrouping happens.
The same board subtracts. When the top digit is smaller, a ten has to be opened, and the board shows it being opened. Later rungs add thousands, then decimals, on the same columns.
What it teaches
- Two-digit plus one-digit, carrying
- Two-digit addition with carrying
- Three-digit addition
- Two-digit subtraction, borrowing
- Three-digit subtraction
- Adding and subtracting decimals
Mistakes it recognises as your child plays
- Forgetting the carried ten
- Carrying into the wrong column
- Taking the small digit from the big one
- Borrowing without taking one from the next column
- Borrowing from a zero without going further left
- Adding decimals without lining up the point
See what it finds.
Carry is also one of the games in the five-minute subtraction with regrouping (borrowing) check, which plays several tiles, picks the next problem from the last answer, and names the pattern it sees.
The other tiles
Stacks · Make Ten · Chart · Odometer · Time · Fraction · Brick · Rectangle
Cardinal Math watches for all of these, every day.
Inside the app the same patterns are caught as your child plays, across the whole of K to grade 5, and explained to you in plain words. One price, no ads, no streaks. Coming to iPhone and iPad.
Tell me when it's out