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Lesson 11 — Activity 1: Length
Lesson 11 — Activity 1: Length
Getting Ready:
The metric system is a system of measurement. It was created so that people around the world could have a standard system. The metric system is sometimes called the SI system. This refers to System International, more commonly known as Standard International Units.
The Imperial System is also a system of measurement. It was the traditional system of weights and measurements which was developed in Great Britain and used from 1824 until the adoption of the metric system beginning in 1965. You will look at both systems in this theme.
Think about what you know about the units which measure lengths.
Try This:
Which is longer?

A
mile
or a kilometre?

A yard
or a
metre?

An inch or a centimetre?
A mile is longer.
A
metre
is longer.
An inch is longer.
This lesson will focus on the metric system. First we will look at length measurements.
To begin, there are seven main levels of measure within the metric system. The prefixes do not change whether you are talking about length, mass, or volume.
The basic unit of length in the metric system is one metre. Most classrooms have a metre stick in them. You have probably worked with a metre stick.
Look at the chart below:
LENGTH  
millimetre (mm) 
centimetre (cm) 
decimetre (dm) 
metre (m) 
dekametre (dam) 
hectometre (hm) 
kilometre(km) 
Notice the italicized parts of the words on the chart. These are the prefixes that tell how many of the base units you have.
The metric system is based on groups of ten. For example, there are ten metres in a dekametre and ten dekametres in a hectometre. This makes converting between different metric units very easy!
One of the easiest tools to do this with is to use the stair method. This involves moving the decimal in the number that you are working with one place for every stair. (The basic unit stair in the chart below is the metre.)
(kilo — km; hecto — hm; deka — dam; metre — m; deci — dm; centi — cm; milli — mm)
For example, if
you have a tractor that is 650 centimetres long and want to know how
many metres long it is, you can figure it out like this:
It is 2 steps up from centimetres to metres. Since you are going up the stairs, you will move the decimal place 2 places to the left in your number. Since your number doesn't have a decimal showing, put it at the end of the number and then move it.
650. becomes 6.50
This tells you that the tractor is 6.5 metres long!
What if you had a room in your house that was 6.7 metres long and you wanted to know how many millimetres it was?
From metres (basic unit) to millimetres is 3 steps down the stairs, so you will move the decimal 3 places to the right.
6.7
Notice that you don't have enough numbers to move the decimal 3 places. When this happens, add zeros into the blank spots.
6.700
6.7 metres is 6,700 millimetres long!
Try This:
What if you had measured the length of an object and found out it was 12,345,678.9 mm long and you wanted to know how many km long it was? From mm to km is 6 steps up. You will move the decimal place 6 places to the left. Try it!
12,345,678.9 becomes 12.3456789 km long.
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