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A group of mice, robins, hedgehogs and owls have made a seesaw in the woods.
Use the interactive seesaw below to have a play with them.
To put an animal on the seesaw, drag it towards a seat. When the seesaw changes colour slightly, you will know the animal is in the right place.
How can you make the seesaw balance?
Try exploring to find lots of different ways.
What else can you discover?
We would love to hear what you find out.
This article, written for students, looks at how some measuring units and devices were developed.