Topics · Numbers & Calculations
Adding and subtracting
Add and subtract big whole numbers, and use the tricks the operations hide.
From scores to savings, adding and taking away never stops.
More ways into this idea
- Play with itPlace Value MachinePile blocks into columns, trade tens, pull the ×10 lever
- Make it a gameAbout How Much?Throw a net over the number line before you calculate
- Make it a gameNumber BuilderBuild big numbers from place-value pieces — and trade them
- Test yourselfA fresh mixed set, whenever you likeExplanations after every question. Nothing is recorded.
Common sticking points
- A common sticking point is losing the regrouped ten — the little 1 above a column is a real ten, not decoration. (You may know this as 'carrying'; Brilika teaches it as regrouping.)
- Another is flipping columns in subtraction — always taking the smaller digit from the larger. Regrouping fixes it: unpack a ten (or a thousand, step by step) so the top has enough.
- Subtracting across zeros can look like magic nines. It isn't: each 9 is a ten-for-one trade with a real source, one place at a time.
Try this together
Ask: what is 5 002 − 4 998? Before any regrouping, try counting UP from 4 998. (It's 4 steps!) Talk about when the long method is worth it — and when counting up wins.
1–5 minutes, no materials to buy, nothing to hand in.
Ontario curriculum details
- B2.1Use properties of the operations to solve problems
- B2.4Add and subtract whole numbers to 100 000
Plain-language summaries. See the full curriculum for every expectation and the official source.