Lesson 4 of 15
Going back to the side you started from
Show on a big screenA square patch has 361 tiles. How long is its side? The sign √ finds a square's side from its tiles. √361 is the side of this patch.
Step 1 of 4
- 8 × 8 = 64 — squaring the side.
- Going back: √64 = 8.
- A common wrong guess: √16 is half of 16, so 8.
- Check: 8 × 8 = 64, not 16. So √16 = 4.
The side is 19 tiles, so √361 = 19. Check: 19 × 19 = 361.
Rule: A square root is the side of a square. Check it: multiply the side by itself.
- √1 = 1, √9 = 3, √36 = 6
- √100 = 10, √121 = 11, √225 = 15
(−9) × (−9) = 81 too. So 81 has two roots, 9 and −9. A side cannot be below 0. So here we use the positive one: √81 = 9.
Slide the side until the tiles match the area.
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Try the lab to finish this lesson.