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Spark & Whetstonethe grown-up commons

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Why the Formula Works

Four rules most of us learned without a reason, rebuilt with paper: long multiplication as a rectangle, dividing by a fraction, cross-multiplying and completing the square.

For grown-ups, from what GeometryForge teaches children at Spark & Anvil.

  1. Lesson 1Multiplication is a rectangle
  2. Lesson 2Dividing by a fraction
  3. Lesson 3Cross-multiplying
  4. Lesson 4Completing the square
At the table · a grown-up and a teenager

The scissors proof

You'll need: squared paper, scissors, a pencil.

  1. The grown-up picks one rule from school they never understood.
  2. Together, find the drawing in this course that explains it and cut it out of squared paper.
  3. The teenager explains the drawing back to the grown-up in their own words, without the formula.

Print the guidebook (all lessons + the table activity) →