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Students find the distance between points on a number line by counting and by using subtraction. They then use subtraction to find differences in temperatures.Students discover that the distance between any two points on the number line is the absolute value of their difference, and apply this idea to solve problems.Key ConceptsStudents know from earlier grades that the distance between two positive numbers on the number line can be found by subtracting the lesser number from the greater number. For example, the distance between 5 and 11 is 11 – 5, or 6. We can also state the rule for finding distance as “The distance between two positive numbers is the absolute value of their difference.” With this version of the rule, we don’t have to consider which number is greater; the result is the same either way. Using the example of 5 and 11, the distance is |11 – 5| or |5 – 11|, both of which are equal to 6.This idea extends to the entire number line, including numbers to the left of 0. That is, the distance between any two numbers is the absolute value of their difference. For example, the distance between –5 and 3 is |–5 – 3| = |–8| = 8 or |3 – (–5)| = |8| = 8, and the distance between –12 and –7 is |–12 – (–7)| = |–5| = 5 or |–7 – (–12)| = |5| = 5.Goals and Learning ObjectivesUnderstand the relationship between the distance between two points on the number line and the difference in the coordinates of those points.Find distances in real-life situations.