Hi, everyone! If you haven't met me, my name is Alice (the cow), and I'm trying to help my nephew, Fred to learn all about how to measure things. Today, I thought I'd give him an introduction to metric units. I wonder if you can help me out.

Right, Fred. Humans like to count in powers of ten because they have ten fingers. The main powers of ten you need to know are 10, 100 and 1000. It's a bit trickier for us, with our hooves, but you'll eventually get used to it. I did!

One thing we cows know a lot about is milk. So, Fred let's start off by talking about how to measure milk. The main units for measuring liquids are:

• Millilitres (abbreviated mL)
• Litres (abbreviated L)

The smallest of these units is the millilitre.

• You know that dropper that Farmer Jones uses to give you your eye drops? About \(20\) drops of that will make up one millilitre.
• 5 millilitres of milk will fit into this teaspoon, so you can imagine how small a millilitre is.
• When I'm milked, I produce about \(11\) mL of milk with each squirt.
• A glass of milk contains about \(250\) mL of milk, and I'll produce about \(350,000\) glasses of milk in my lifetime.

Well millilitres definitely aren't enough to measure the amount of milk I produce each day. We need a bigger unit, and that is the litre (abbreviated as L). There are \(1,000\) mL in \(1\) L.

• My milk is sold in cartons at the supermarket. Each carton holds 1 litre.
• The milking bucket on the right holds about \(10\) L of my milk. That's enough for \(40\) glasses of milk!
• Fruit juice and other liquids are also sold in one or two litre cartons or bottles. Can you check them out for me next time you're at the supermarket and tell Fred what you've found out next time you come over to the farm?

Are you munching on raisins again, Fred? You'll spoil your dinner! How about eating an apple instead?

• Each of those raisins you're eating has a mass of about \(1\) g.
• Small apples have a mass of around \(150\) g.
• Butter is usually sold in \(250\) g packets.
• No Fred, you're way too heavy for me to measure your mass in grams! We'll have to use bigger units.

• 6 small apples have a mass of 1 kg.
• Our friends here probably have masses around 40 kg.
• Fred, your mass is about 120 kg.
• My mass is around 750 kg.

We measure mass using scales. There are different scales for measuring different ranges of masses. For example, kitchen scales measure masses in the range from 0 to 2,000 g. Bathroom scales measure masses in the range from 0 to 180 kg. Don't get on those kitchen scales, Fred! You'll break them!

• Eric has a mass of about \(5\) tonnes. t is short for tonne, so we can write this as \(5\) t.
• A car has a mass of about \(2\) t.

• A pin (used in sewing) has a diameter of about \(1\) mm.
• An Australian 10 cent piece is about \(2\) mm thick.
• A New Zealand 10 cent piece is about \(1.5\) mm thick.

• A Christmas Beetle is about \(2\) cm long.
• I am about \(117\) cm tall.
• Our friend, Sam's desk is about \(65\) cm wide.

• I'd like to learn to play the didgeridoo. This didgeridoo is about \(1\) m long, but I'm looking for a slightly longer one as I'm told that longer didgeridoos make a deeper sound.
• My 4 year old friend, Timmy, is about \(1\) metre tall.
• The Adelaide Oval is about \(167\) m wide.

If you want to measure the distance between cities like Sydney and Perth, you need to use a bigger unit again. The preferred metric unit is the kilometre (abbreviated km).

We measure temperature using degrees Celsius (\({}^\circ C\)). Here are some common temperatures:

• Water freezes at \(0^\circ C\). Snow is frozen water, so it needs to be below \(0^\circ C\) for the snow to stick around, Fred. That's why it's so cold here at the snow.
• A hot summer's day might have a temperature of between \(30^\circ C\) and \(40^\circ C\).
• Water boils at \(100^\circ \) Celsius.
• I set the oven to a temperature of \(180^\circ C\) to make your favourite chocolate cake.