Topics
10. Measurement
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Australia
Year 3

10.05 Order and compare mass

Lesson
Practice
Lesson

Are you ready?

We need to remember how to  order numbers  to help us in this lesson.

Examples

Example 1

Order these numbers from largest to smallest.

a

73, \, 33, \, 37

Worked Solution
Create a strategy

We should order the tens first, then the ones.

Apply the idea

The numbers in the place value table are shown:

TensOnes
73
33
37

37 and 33 have the same smallest tens digit, so they are smaller than 73.

But 33 has the smaller ones digit, so 33 is smaller than 37.

The numbers from largest to smallest are: 73,\,37,\, 33

b

671, \, 167, \, 617

Worked Solution
Create a strategy

We should order the hundreds first, then the tens, then the ones.

Apply the idea

The numbers in the place value table are shown:

HundredsTensOnes
671
167
617

167 has the smallest hundreds digit so it is the smallest number.

671 and 617 have equal hundreds digits, but 617 has the smaller tens digit.

The numbers from largest to smallest are: 671,\,617,\, 167

Idea summary

When we use place value to order numbers, always start with the highest place value.

Order objects by mass

We could weigh each object in a group to put them in order but we could also use balance scales. We can work out which object is heavier or lighter out of two objects, then compare it to another object.

In the video, we will use the mass to compare objects, as well as balance scales.

Loading video...

Examples

Example 2

We want to order these animals from lightest to heaviest.

This image shows three weighing scales with three birds on it. Ask the teacher for more information.
a

Which of these animals is the heaviest?

A
Sparrow
B
Cockatoo
C
Pigeon
Worked Solution
Create a strategy

The heaviest animal will be the one with the largest number on the scales. Plot the weights of the animals on a number line.

Apply the idea

The three weights are plotted on a number line below.

0100200300400500600700800

Based on the number line, the number line shows that the cockatoo is the heaviest among the three. So the correct answer is option B.

b

Which of these animals is the second lightest?

A
Sparrow
B
Cockatoo
C
Pigeon
Worked Solution
Create a strategy

The second lightest animal will be the one with the second smallest number on the scales.

Apply the idea

Based on part (a), the number line shows that the pigeon is the second lightest animal. So the correct answer is option C.

c

Which of these animals is the lightest?

A
Sparrow
B
Pigeon
C
Cockatoo
Worked Solution
Create a strategy

The lightest animal will be the one with the smallest number on the scales.

Apply the idea

Based on part (a), the sparrow is the lightest among the three. So the correct answer is option A.

Idea summary

To put objects in order by mass, we need to make sure we are using the same unit of measurement, such as grams, for each object we are comparing.

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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