Stage 1 · The World of Numbers / #2
Is 3×4 the Same as 4×3?
S-1 · Numbers are amounts S-4 · Shapes can move S-5 · Patterns can be put into words S-6 · Mistakes are fine — try it
Coming soon
The video is in production. Follow along on GitHub to hear when it is out.
The idea
Turn the whole dot array and three rows of four become four rows of three, with not one dot gained or lost, so three times four equals four times three.
A common mix-up
Three fours and four threes are different things, so they might not be the same amount.
Where it stops working
Subtraction can't swap: five take away two leaves three, but two take away five isn't possible.
School year
China 2 US 2–3 UK 2 Singapore 2