Topics
10. Measurement
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Australia
Year 3

10.04 Measure and estimate mass

Lesson
Practice
Lesson

Are you ready?

Think about a feather and an elephant. Which one of those items do you think would be heavier?

Units of mass

This video introduces the units of grams, and kilograms and discusses the types of objects that would be measured by these units.

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Examples

Example 1

Which unit is best to measure the mass of this cup of flour?

This image shows a cup of flour.
A
Kilograms
B
Grams
Worked Solution
Create a strategy

Remember that 1 kilogram is equal to 1000 grams.

Think about these examples to help you.

ObjectBest unit
Bar of chocolateGrams
PersonKilograms
Apply the idea

A cup of flour is small and light like a bar of chocolate.

So the correct answer is B: Grams.

Idea summary

A gram has a mass similar to a piece of paper, or a feather. A kilogram has a mass similar to a 1 litre bottle of milk or juice.

The prefix can help with identifying the size of the units.

kilo - means "one thousand of", so a kilogram has 1000 grams.

Scales

This video looks at measuring the mass of objects using a scale.

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Examples

Example 2

The scale below shows an object balanced evenly with a particular set of weights.

This image shows a scale that evenly balances an object and weights.

The following weights were on the scale:

This image shows 1 5 kilogram weight, 2 2 kilogram weights, and 3 1 kilogram weights.

What is the total mass of the object?

Worked Solution
Create a strategy

Find the total mass by adding all the values on the given weights.

Apply the idea

We can see there is one 5\text{ kg} weight, two 2\text{ kg} weights and three 1 \text{ kg} weights.

\displaystyle \text{Object}\displaystyle =\displaystyle 5+2+2+1+1+1Add the values
\displaystyle =\displaystyle 5 + 4 + 3Add the 2s and 1s
\displaystyle =\displaystyle 12 \text{ kg}Add the values
Idea summary

We can measure the mass of objects with different types of scales. Mechanical scales are just like a number line, but in a circle.

Outcomes

AC9M3M01

identify which metric units are used to measure everyday items; use measurements of familiar items and known units to make estimates

AC9M3M02

measure and compare objects using familiar metric units of length, mass and capacity, and instruments with labelled markings

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