Organize students to work with a partner and pose the following problem:
- Professor Peabody decided to visit International Falls, Minnesota during the winter. He took a plane from Arizona to Minnesota. When he left Arizona, the temperature was 58°F. When he arrived in Minnesota, the temperature was –12°F. What was the difference in the temperature?
As students are working, circulate and identify students who will share their solution strategy.
- Show how you solved this problem. (Possible response: First I made a number line from –15 to 60. Then I put a mark at 58° on my number line,
and another mark at −12°. Next I counted the hops between the two marks and got 70.)
- [Student name] thought the answer would be 46 since the difference of 58 − 12 = 46. Do you agree or disagree? Explain your thinking. (Possible response: I disagree. [Student name] is not considering that −12 is below zero. The distance between 0 and 58 is 58, and the distance between 0 and −12 is 12. So the distance between −12 and 58 has to be more than 58, not less.)
