In this unit we explore the size of a metre and develop our own ways to estimate a metre length.
- Recognise the need for a standard unit of length.
- Recognise a metre length.
- Estimate and measure to the nearest metre.
When students can measure lengths effectively using non-standard units, they are ready to move to the use of standard units. The motivation for moving to this stage, often follows from experiences where the students have used different non-standard units for the same length. They can then appreciate that consistency in the units used would allow for the easier and more accurate communication of length measures.
Students measurement experiences must enable them to:
- develop an understanding of the size of the standard unit;
- estimate and measure using the unit.
The usual sequence used in primary school is to introduce the centimetre first, then the metre, followed later by the kilometre and the millimetre.
The centimetre is often introduced first because it is small enough to measure common objects. The size of the centimetre unit can be established by constructing it, for example by cutting 1-centimetre pieces of paper or straws. Most primary classrooms also have a supply of 1-cm cubes that can be used to measure objects. An appreciation of the size of the unit can be built up through lots of experience in measuring everyday objects. The students should be encouraged to develop their own reference for a centimetre, for example, a fingertip.
As the students become familiar with the size of the centimetre they should be given many opportunities to estimate before measuring. After using centimetre units to measure objects the students can be introduced to the centimetre ruler. It is a good idea to let the students develop their own ruler to begin with. For example, some classrooms have linked cubes which can be joined to form 10 cm rulers. Alternatively pieces of drinking straw could be threaded together.
The correct use of a ruler to measure objects requires specific instruction. The correct alignment of the zero on the ruler with one end of the object needs to be clarified.
Metres and millimetres are established using a similar sequence of experiences: first construct the unit and then use it to measure appropriate objects.
- Begin the session by acting out the following scene with the students.
A small play
Crew/ Cabin boys & girls…..Class
Treasure…..A small box
Crooked palm tree…..Desk
Captain Blood, the pirate decided to bury his treasure.
He started from the crooked palm tree and carefully counted 12 steps, (heel, toe) and then stopped and placed the treasure on the ground.
To make sure that he remembered where he left it he wrote down on his map 12 steps.
He wanted to make really sure that he had measured correctly before digging the hole so he asked a cabin boy or girl to check.
Captain Blood was puzzled how could the cabin boy/girl have a different number of steps.
Had he made a mistake?
- Discuss with the students the reasons for the differences.
Can you think of a measure that Captain Blood could use that is the same for everyone?
If the students come up with the suggestion of a metre, ask:
How long is it?
When and where is used as a measurement?
For the next four days the students will spend time making and measuring metres.
- Tell the students that Captain Blood is really interested in using metres on his map but he’s not sure how long, wide or high a metre is. He wants his crew to go around the island (classroom), and make a list of all the things that are less than one metre, about one metre and more than one metre and then share it with him so that he can learn about a metre.
- Provide the students with a metre stick or a one metre length cut from ribbon or cardboard.
When students are measuring encourage them to measure height, depth, width and girth.
- At the conclusion the students can share their findings with the crew and Captain Blood and find out if they had similar measurements for objects in the room.
- Finally they could measure from the crooked palm tree to the treasure and record the answer in metres. The letter m could be introduced as a means of recording. Suggestions on how to record incomplete metres could also be discussed.
- Tell the students that Captain Blood has decided that now he knows what a metre is he wants to start drawing up plans for his new pirate ship and that he would like the crew to help.
Discuss with the students the type of boats that pirates sailed in.
Provide them with chalk a metre measure and take them outside to draw the boat to Captain Blood’s requirements.
Measurements of Captain Blood’s New Pirate Ship
- Length ………..10 metres
- Middle mast……5 metres
- Front/Back mast..4 metres
- Plank……………1 metre
The students might like to add extras; flags, anchor ropes, cannons etc and add them to the measurement list.Encourage students to estimate before drawing.
- Ask the students to stand and show how high they think a metre would be from the floor. Check with their metre measure and reference it to their body.
A metre is as high as …………….(my ribs).
How wide is a metre? A metre is from my fingertips to ……………
- Ask the students to estimate how many of their handspans would be the closest to a metre.
Trace an outline of their handspan on to paper and then cut it out and use it to measure along the metre. Record results. Have the students estimate how many of their footprints would be closest to a metre. Make outlines by removing their shoe and tracing around their foot.
Check how students position the shapes when measuring. Do they begin from the same baseline?
Do they use the measuring unit consistently without gaps or overlapping?
The students can show their results by pasting their outlines on to paper and recording the number beside it.
To measure 1 metre it takes: ____ of my handspans _____ of my footprints
To finish pose this problem for the crew,
Captain Blood has gone to a boat shop to buy some new canvas for sails. He wants two metres. Can you show me using a body measurement how long two metres would be?
- Captain Blood has decided to have a sports day for the pirate crew.
The events for the day are:
Toss the cannon ball (1kg of clay wrapped in plastic wrap)
Jump from the Plank ( A standing jump from a rectangular piece of cardboard)
Metre Kick (A rugby ball)
Set up the activities in the three stations
When the students share their results at the end, talk about the half metre, or the extra bit and the need to have a smaller unit of measure.The students will need to work with a partner who can stand where the rugby ball lands after the kick - As above, have the students record their estimation prior to measuring. - After tossing the cannon ball the students estimate how many metres and then measure. Encourage them to use heel toe stepping.
- Exploration of a metre ruler
Provide the students with a standard metre ruler. Look at the markings on it and discuss what they can see.
Talk about where you begin measuring from. (Students can have difficulties identifying the starting points on calibrated rulers. They start from the edge rather than the markings.)
If the students haven’t offered the word centimetre in discussion explain to them that the space between the numbers is one centimetre and place centimetre cubes along the ruler.
Ask: How many centimetre cubes might fit along the metre?
If 1cm cubes that connect are available join 100 using two different colours to distinguish the decades. Place the line of cubes on top of the metre ruler and count in tens to 100.
Provide the students with string, scissors and PVA glue and let them investigate the different ways of creating patterns with 1 metre of string. The students first measure a metre and then make a pattern.
Glue their discoveries to cardboard and display the one-metre patterns.
Discuss that different patterns look as though they have different lengths.