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## 'Choose Your Units' printed from http://nrich.maths.org/

Some units are particularly well suited to a given measurement because they turn out to give a small, whole number of units. Understanding this concept gives you a feel for the order of magnitude of the quantities.

What units would you measure these quantities in to make an approximation which was a reasonably small whole number?

- The volume of a bacterium
- The mass of an oak tree
- The area of a leaf
- The half-life of Uranium-235
- The area of a football pitch
- The average lifespan of a human
- The volume of a bath tub

Can you reverse the process? For the following units, what physical phenomena might naturally be measured to be around 1 unit?

- Millimetre
- Newton
- Angstrom
- Joule
- Volt
- Microgram
- Micrometre
- Hertz
- Parsec

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