- Students are asked what they know about length
- A drawing of two curved snakes is displayed for
the class. One snake has lots of little curves while the other has one
big curve. Students are asked to
guess which snake is longer. They
are then asked for ideas on how to prove one snake is longer than the
other.
- Students are given the following materials:
paper, ruler, string and paper clips (NO STANDARD RULER). Students come up to the drawing to
offer their solutions using any of the given materials. Others are asked to agree or offer
another solution.
- Once several methods are discussed, divide the
class up into groups, each group working on a different method (one
group uses paper clips, one group uses string, etc.). The worksheet [attached] has 4
drawings of snakes. Students are
asked to order the snakes from longest to shortest. They then test their estimates using
the method they created together.
The paperclip group could have the option to work on the large
snakes (since the paper clips are two big for the worksheet snakes)
- Groups share their answers with the rest of the
class. Misconceptions are
discussed.
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- It is measured in cm or in
- We use a ruler to measure it
- It is how long something is
- I think the red one is longer because it is
curvier
- I think the black one is longer because it has
that one big curve.
- We could make a ruler to measure the length
- We could line up paper clips to measure how
long each one is.
- I made a ruler and measured that snake to be 23
centimeters
- Do we fill the snake head with paper clips?
- I made a ruler and my
group member made a ruler also, but we got different answers. (Put the 1
in different positions)
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- Does it have to be
measured in cm or inches? What about using the length of my hand?
- Emphasize the fact
that the only way to decide which one is longer is to measure them both.
- Note that there are
several ways this problem could be solved with the given materials.
- Begin to use a
ruler. “What do we do with this
curve? How can we measure a
curve?
- How do you know your
ruler has centimeters on it?
Could you call it by a different name?
- Remind students what
they are measuring
- Investigate the two
rulers in a large scale on the board.
Ask the rest of the class for input. Compare the made rulers to a real
ruler.
- Allow students to
discuss whether or not they think each group measured accurately.
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