More digits | Crosswise | ABC of Mathematics

ABC of Mathematics

Fields

Programming & Computer Science 2 open
Mathematics 4 open

Try a lesson

Build an Interpreter Programming
Build Hangman Programming
Invent Counting Math
Invent Place Value Math
Invent Arithmetic Math
Invent Negative Numbers Math

Coming next

Build a Compiler Programming
Invent Sets Math
Build a JavaScript Runtime Programming

Not sure where to begin? Start with Build an Interpreter or read how the lessons work

You logged in, out, or switched accounts in another tab. Changes on this page are not being saved.

This site was updated in another tab. Changes on this page are not being saved.

This site is open in another tab with an older version, and this page cannot load until it is gone. Close or reload your other tabs of this site.

Math › Invent Arithmetic › Crosswise

Break it up Parts in boxes Break up again

The short way Each total in full In your head, from the left Make one number round

Any order you like Pair them up Always, or only sometimes?Name the move

One for ten Where are the ones?Trade on paper Keep the gap Do the laws hold?

Rows of pebbles Count the tray Laws of times Count on Fill the table

Cut the rectangle Times ten Cut the tray Times one digit On paper

Crosswise Four pieces Level by level More digits Carry as you go

Double it A table of doubles Double and add Every number?

The fair Check the bill Set a price Lunchtime Close the box

Loading...

ABC of …

© 2026 Debjit Biswas · debjitbiswas.com

Programming Math About Privacy Terms

May we use a cookie to count your repeat visits? It shows us which lessons work. No ads, no tracking across sites. Details