Use the open number line and our lists of temperature extremes to make signed number operations and absolute value sensible. Students compare record high and low temps (integers) and use absolute value in order to always find the positive difference. Subtraction of negatives becomes obvious in this lesson.
The deflated ball controversy makes an interesting segue into negative number line understanding. A particular digital psi football gauge reads 0 when the ball is at a proper NFL inflation of 13 psi. Footballs inflated under 13 psi produce negative psi readings…