Weather and Negative Numbers
Purpose: students will discover a meaningful application
for negatives; students will use variables in a real technology based
setting; students will create meaningful graphs.
Materials: Indoor/Outdoor Thermometer, Computer with Spread
Sheet (eg: Microsoft Excel, Open Office Calculate)
Background: This lesson was used in an urban seventh grade
to present negatives in a pre-algebra class. There was only one
thermometer and one Macintosh 5200 with Claris Works available.
Reformatted January 2010
- Place an indoor/outdoor thermometer by the window
- Assign a "meteorologist" to read the temperatures
daily and record them using a spread-sheet. Train the
student to use columns in the spread-sheet consistently
(Eg: column A: represents today's date, B represents the
inside temperature, C represents the outside temperature,
D represents the difference.)
- Train the meteorologist to use the cell variables to
determine the difference (eg: '= B5 - C5 ')
- Each day, have the meteorologist report to the class
the temperatures and the difference. (To let all students
get a chance, change the meteorologist each week and have
the previous one train the new one)
- When the temperature outside drops below the
temperature inside the spread-sheet will report a
negative number. At this point ask the meteorologist
"What does the negative mean?" Most students will quickly recognize that the negative means that its colder outside.
- Once the students are comfortable with using the
spread sheet add a new column for the difference between
yesterday's temperature, and today's (eg: '= C11 - C10).
Students should see that a negative here means the
temperature has dropped.
- Use the spread sheet chart option to create a graph.
Discuss with the students, "should the lines be falling
or rising this time of year (spring or autumn)?" "Do we
see that happening, why/ why not?"
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