M1 Measurement : Length

MEASUREMENT

    ~ a process that uses numbers to describe a physical quantity based on what we can observe.
                  
               

   ~ finding a number or value to show the size of amount of something.

                   

Why do we measure ‘things’?

  

     ~ to be able to compare things to each other.

     ~ to calculate/gauge

     ~ cooking properly with the right amount of ingredient and timing

     ~ taking the right amount of medication

     ~ what else can you think of? J

UNIT OF MEASURE(UOM)

Units of Measurement provide standards for what we measure so that the numbers from our measurements refer to the same thing.

          

Example:

1 metre is a unit of length. We say that the unit of measurement is in metre

[We say measure in metre, and not measure in ‘1 metre’. The ‘1’ is dropped]

LENGTH

~  measurement or extent of something from end to end.

We can use centimetre(cm), metre, kilometer(km) or millimeter(mm) to measure length. 

MEASURING LENGTH

 Using cm: The length of the red line is 5cm.

           

   
Using metre: Usain won the Gold for the 100m race

    100 m is also the same as 10000 cm or 0.1 km or 100000mm. 

     

Using Kilometre: The distance between BuonaVista and Commonwealth is 1.2km
                          

    The distance is in km and not 1200m or 120000cm or 1200000mm. Why?

    

  Using millimetre : the length of a grain of rice is about 5mm.

       It can also be expressed as 0.5cm, 0.005m or 0.000005 km

COMPARING AND ORDERING LENGTH

Long/Longer/Longest    Tall/Taller/Tallest   Short/Shorter/Shortest

                        

	Long/tall short	Examples The black pen is 20cm long.
Comparative (comparing 2)	Longer/ Taller shorter	(blue pen and black pen) The blue pen is 3 cm longer than the black pen. -> The blue pen is 20+3 = 23 cm long. (red pen and black pen) The red pen is 4 cm shorter than the black pen. -> The red pen is 20-4 = 16cm long.
Superlative (Comparing 3 of more)	Longest/ Tallest shortest	(blue pen, black pen, red pen)  Blue pen is the longest. Red pen is the shortest.

Kilometre/metre/centimetre/milimetre (UOM)

1 km = 1000 m

1 m = 100 cm

1 cm = 10 mm

   km-->m-->cm--mm ( x )  

LENGTH

From km to m to cm to mm

km      (x1000)      m      (x100)   cm   (x10)   mm     

           1km        =      1000m        =     100000cm    = 1000000 mm      

Eg:  3m = 3 x 100 = 300cm  = 300 x 10 = 3000mm            

Eg : 2km = 2 x 1000 = 2000m 

                2km = 2000m = 2000 x 100 = 200000cm

From mm to cm to m to km   

km     (/1000)   m (/100)        cm.    (/10)   mm          

Example:  400cm =  400/100 = 4m ( 4/1000) = 0.004km

                400cm = 4m = 0.004km

  Converter:    (divide) / <-   km m(1000) cm(100) mm (10)  -> x (multiply)

Example

Convert 5km to m

          / <-   km m(1000) cm(100) mm (10)  -> x   Step 1: Write 'Converter' 

                5km =      m                              Step 2 : Underline UOM , x or /? 

    5km = 5 x 1000m                    km to m-> x

                       = 5000m                                   Step 3: x 

Example:

Convert 250m to mm

      / <-   km m(1000) cm(100) mm (10)  -> x   Step 1 : Converter

          250 m =           mm          Step 2:  Underline UOM x or / ?

          250 m = 250 x 100 x 10                                       m to mm -> x

    = 250 000 mm                         Step 3 : x         

Example:

Convert 0.7km to cm

    / <-  km m(1000) cm(100) mm (10)  -> x   Step 1 : Converter

          0.7km =       cm

          0.7km = 0.7 x 1000 x 100                  Step 2:  Underline UOM, x or /? 

    = 70000cm                     Step 3 : x          

Example:

Convert 1.5 m to km

    / <-  km  m(1000) cm(100) mm (10)  -> x   Step 1 : Converter

          1.5m =       km     Step 2:  Underline UOM, x or /?

               = 1.5 / 1000                                  <-   divide

    = 0.0015 km               Step 3 : /          

  

Example:

Convert 250mm to m

   / <- km  m(1000) cm(100) mm (10)  -> x   Step 1 : Converter

          250mm =        m     Step 2:  Underline UOM, x or /?

                   = 250 / 1000 x 10                                <-   divide

            = 0.025m      Step 3 : Calculate          

“It was identified that children had difficulties understanding the concept of starting from a fixed point when dealing with length (O’Keefe and Bobis, 2008).”