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Measuring Up Prototypes for Mathematics Assessment (1993) / Chapter Skim
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Lightning Strikes Again
Pages 115-124

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From page 115...
... background/: This task assumes that chi~ciren have had experience in solving complex problems that are posed in the context of a map. In particular, they should have used rulers to measure distances on a map and dealt with converting from map distances to real distances.
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From page 116...
... . Before passing out the student activity materials, the teacher should conduct a short discussion of lightning, focusing especially on the fact that often you see the flash of lightning before you hear the thunder clap.
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From page 117...
... Because sound travels more slowly than light, they did not hear the thunder right away.
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From page 118...
... 5. Now suppose lightning strikes again at a different place.
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From page 119...
... The person at point C heard the thunder from that same lightning bolt ~ 5 seconds after the lightning struck. Show where the lightning could have struck.
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From page 120...
... . Although the immediate relevance of lightning depends somewhat on what part of the country one happens to live in, the phenomenon of nature will be familiar to all students.
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From page 121...
... If the ch i ~d has already indicated the perpendicular bisector of segment AC for question 5, then the proper answer to question 6 is "no." On the other hand, there is nothing wrong with answering question 5 with a single point equidistant from A and C, and in that case, the proper answer to question 6 is "yes," followed by a description of the perpendicular bisector. If, instead, question 6 were worded as "In question 5, where else could lightning have struck?
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From page 122...
... At the highest level, the perpenclicu~ar bisector of segment AC is described as the possible location for the lightning strike in question 6, although use of the geometric term is not necessary. A circle of radius 1" is drawn around point A for question 7.
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From page 123...
... The p ri n c i pa ~ ~ iffe re n ce between the high and medium response is that the latter does not consicler many possible locations for the lightn ing strikes. One point equ id istant from A and C is found for question 5, but the answer to question 6 is"no." Characteristics of the low response: The low response is characterized by thinking that is limited to one point or one distance at a time.
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Key Terms

  • perpendicular bisector
  • sound travels
  • lightning strike
  • proper answer
  • task design

  • suppose lightning
  • geometric ideas
  • rough calculations
  • immediate relevance
  • somewhat lower

  • answering question
  • discuss questions
  • relatively rough
  • bring additional
  • short discussion

  • lightning struck
  • lower level
  • thunder clap
  • occur simultaneously
  • relatively difficult

  • depends somewhat
  • map distances
  • concepts involved
  • numerical distractions
  • focusing especially

  • activity materials
  • labeled dots
  • lightning depends
  • drawing little
  • medium response


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