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The Situation

 
The Challenge(s)
  • How much did the temperature drop?

 

Question(s) To Ask
These questions may be useful in helping students down the problem solving path:

  • What is a guess that is too low?
  • What is a guess that is too high?
  • What is your best guess?
  • Why are there two 20’s on each side of the thermometer?
  • How can we tell whether the temperature is positive or negative?
  • How can we determine what the temperature is?
  • What units are we measuring temperature with?
  • How can we figure out what the temperature is when it is not precisely on the line?

 

Consider This
This problem is essentially a real world version of the classic temperature drop absolute value problem.  That kind of problem usually states something like, “At 1 PM the temperature was 35° F and by 10 PM the temperature had dropped to -8° F.  How much did the temperature drop by?”  Some of the notable differences between this and the textbook version include:

  • The temperature units are intentionally unspecified to create some productive classroom debates when there are two different correct answers because some students may use the Celsius scale while others may use the Fahrenheit scale.
  • The exact numeric temperature values are not given so students will have to read them off the thermometer.
  • There are no negatives on the thermometer, so students will have to use context clues to help them determine which values should be negative.
  • The problem is slightly more engaging as a video clip rather than a text description.

As for the background on this video clip, the thermometer was taken out of a warm room and filmed outside in the cold.  It’s been sped up to show 15 minutes of video in 1 minute.  The white stuff towards the bottom of the video is snow.

To me, it appears that the temperature drops:

  • 44° C (from 17° C to -27° C)
  • 79° F (from 62° F to -17° F)

 

I have also included a printable PDF of the thermometer below in the “Download files” link for use with this lesson.

 

Content Standard(s)
  • CCSS 6.NS.7c Understand the absolute value of a rational number as its distance from 0 on the number line; interpret absolute value as magnitude for a positive or negative quantity in a real-world situation. For example, for an account balance of –30 dollars, write |–30| = 30 to describe the size of the debt in dollars.
  • CCSS 7.NS.1c Understand subtraction of rational numbers as adding the additive inverse, p – q = p + (–q). Show that the distance between two rational numbers on the number line is the absolute value of their difference, and apply this principle in real-world contexts.

 

Source(s)

 

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9 Comments

  1. The thermometer in the downloads has the F and C on switched sides from the video. Just an FYI for anyone going to use it, don’t want to confuse the students.

    • Hi Claire. I’m not sure what email address you’re using, but this most often happens when the emails are blocked either by a school district’s aggressive SPAM filter or Gmail’s SPAM filter. I’d check there first because if it looks like the form’s submitting, then it should be working. Email me at [email protected] if you still can’t get it to work.

      • I can see the small clip with the thermometer when I download files, but I went to look at the Youtube part where you state “As for the background on this video clip, it comes from this clip on YouTube” and it came up video unavailable. I don’t know if that is a necessary video in the first place, but I just wanted to state that it wasn’t working.

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