Topics
9. Measurement
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Australia
Year 4

9.02 Order and compare length

Lesson
Practice
Lesson

Are you ready?

Can you  order 2 or 3 digit numbers  ?

Examples

Example 1

Order these numbers from largest to smallest.

a

73,33,37

Worked Solution
Create a strategy

Use a place value table.

Apply the idea
TensOnes
73
33
37

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

For the ones of 37 and 33, 3 is less than 7, so 33 is less than 37.

So the numbers in order are:73,\,37,\,33

b

671,167,617

Worked Solution
Create a strategy

Use a place value table.

Apply the idea
HundredsTensOnes
671
167
617

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

671 and 617 have the same hundreds value, so we need to compare the tens.

1 is less than 7, so 617 is less than 671.

So the numbers in order are:671,617,167

Idea summary

We can use a place value table to help us order 2 and 3 digit numbers.

Order objects by length

This video uses an example of tablet screen sizes and compares lengths using a number line.

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Examples

Example 2

Glen is 165 cm tall. Valentina is 144 cm tall. Who is taller?

Worked Solution
Create a strategy

Plot the two values on a number line.

Apply the idea

The heights are plotted on the number line below:

140145150155160165170

The taller person will have the larger height measurement which will lie on the right of the number line. Based on the number line, 165 is larger than 144.

So Glen is taller than Valentina.

Idea summary

When plotting numbers on a number line, the number to the right is the larger number.

Order things

This video shows how we can compare numbers, if the units of length are the same, to order by length.

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Examples

Example 3

A shark is 6 m long, a boat is 19\,m long, a dolphin is 3\,m long, a ship is 25\,m long and a whale is 14\,m long.

Choose the list that puts the items you may find in the water from shortest to longest.

A
Dolphin, Shark, Whale, Boat, Ship
B
Whale, Dolphin, Ship, Boat, Shark
Worked Solution
Create a strategy

Plot the lengths on a number line.

Apply the idea

The lengths are plotted on the number line below.

051015202530

So the numbers from smallest to largest are: 3, \, 6, \, 14, \, 19, \, 25

The list in order from shortest to longest should be: Dolphin, Shark, Whale, Boat, Ship

The correct answer is Option A.

Idea summary

As long as the units are the same, you can compare and order lengths in the same way as we compare numbers.

Outcomes

AC9M4M01

interpret unmarked and partial units when measuring and comparing attributes of length, mass, capacity, duration and temperature, using scaled and digital instruments and appropriate units

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