Stage 1 · The World of Numbers / #4
The Distributive Law Is Just One Cut
Coming soon
The video is in production. Follow along on GitHub to hear when it is out.
The idea
Cut a rectangle of four rows of eight between the five and the three, and the two pieces still make the whole, so five plus three, times four, equals five times four plus three times four.
A common mix-up
Five plus three, times four, is five plus three times four, which is seventeen (only one part gets multiplied).
Where it stops working
Five times three plus four can't become five plus four, times three: five times three is one block and the four squares are loose, so they don't make one rectangle.
School year
China 4 US 3 UK 4–5 Singapore 3–4