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What are kilograms?

When we want to measure the mass of an object that weighs more than 1000 grams we use kilograms.

Kilograms are shortened to ‘kg’.

1 kilogram = 1000 grams

or

1 kg = 1000 g

Using kilograms

Look at the items below. As they are over 1000 grams we can measure them in kilograms.

1. Neera's scooter weighs 5 kg which is the same as 5000 g.

2. Isla's laptop weighs 2 kg which is the same as 2000 g.

3. Troy is baking. He is using a bag of flour that weighs 1 kg.

How do we measure the mass of objects?

A common way of measuring the mass of objects is to use balance scales.

A balance scale works by placing the object you want to weigh on one side and adding gram or kilogram masses to the other side until the scales are level.

Masses for weighing usually come as 0.5 kg, 1 kg, 5 kg, 10 kg or more!

There are other types of scales you can use to measure mass.

You can also use a set of scales showing the mass on a dial with a pointer or digital scales showing the mass as a number.

We can weigh ourselves on scales in kilograms. A small child might weigh about 35 kg and an adult weighs about 80 kg.

Now let's have a look at some questions involving measuring in kilograms.

Example 1

The scooter weighs 5 kg. The laptop weighs 2 kg. How much heavier is the scooter?

5 - 2 = 3

The scooter is 3 kg heavier than the laptop, because 5 is 3 more than 5.

Example 2

A family is going on holiday.

• Dad’s suitcase weighs 18 kg.
• Mum’s suitcase weighs 24 kg.
• Becky’s suitcase weighs 13 kg.

Who has the heaviest case?

Mum has the heaviest case at 24 kg.

How much heavier is Mum’s case than Dad’s?

Mum’s case is 24 kg, Dad’s is 18 kg.

24 kg – 18 kg = 6 kg

So Mum’s case is 6 kg heavier.

Example 3

Which is heavier - a kilogram of feathers or a kilogram of steel?

This is a trick question!

Although steel feels heavier than feathers, a kilogram of each would weigh the same. (There would be a lot of feathers!)

Activity

Take the kilogram quiz!

Game