Lesson 1 of 9
One length everybody agrees on
Show on a big screenTwo people measure one bench with hand spans. They get different counts. A hand span is the width of your open hand. Hands differ in size. So the counts differ.
Drag each slider to resize a hand. Watch the count change. The metre ruler stays at 1.8 m.
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Step 1 of 3
- One metre, measured in Chennai.
- The same length, measured in Mumbai.
- Same length, every time, everywhere.
Standard unit — one fixed length that everyone agrees to use.
A metre is the same length in every city. So two people who use a metre get the same length.
Watch out!
More hand spans does not mean a longer bench. A smaller hand gives a bigger count.
Try the lab to finish this lesson.