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Symmetry

Half a picture decides the rest

Half a kite is drawn on squared paper. The paper is printed with small squares. A fold line runs down the middle. Draw the other half.

Half a figure, drawn on a grid, with a fold line.
Step 1 of 3
  1. Half a figure, drawn on a grid, with a fold line.
  2. Each square has a partner across the line.
  3. Fold it. The other half appears — 6 squares in all.

Every square has one partner

Take a filled square. Its partner is the square it matches across the fold line. The partner is the same distance from the line. It is on the other side, in the same row. Do this for every square.

Why this matters

The partner rule works for a kolam too. A kolam is a floor pattern at a doorstep. Draw one half. Copy it to the other side, square by square.

Watch out!

Sliding a half across is not folding it. Sliding keeps left on the left. Folding swaps sides. Take a square two places left of the line. Its partner is two places right of the line.

Paint the right half in the lab. Then tap Next picture.

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This track

  1. 0 Start here
  2. 1 Fold it, and it matches
  3. 2 Not every middle line
  4. 3 How many fold lines?
  5. 4 Symmetry around us
  6. 5 Matching partway through a turn
  7. 6 Half a picture decides the rest
  8. 7 The big picture
  9. 8 Track quiz

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