Lesson 5

Arm Span vs. Height

Est. Class Sessions: 4–5

Before the Lesson

Measuring in Inches. Use Home Practice Parts 4–5 assigned in Lesson 4 and DPP item R to review measuring in centimeters and inches in preparation for this lesson.

Practice Plotting Points. If your students have not had many opportunities to plot points, ask students to complete the Plotting Points Pictures in the Student Activity Book. Using these pages, students plot points both on and between the lines to create pictures. You can quickly ascertain which students can plot data from the pictures that result.

Picture 2 on the Plotting Points Picture pages shows examples of writing ordered pairs. Review with students that the first number in the ordered pair gives the distance on the horizontal axis and the second number shows the distance on the vertical axis. See the Content Note.

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If students have difficulty tracing the lines to a point with their fingers, suggest they use two rulers to show the point of the intersection of the lines.

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Ordered Pair. When speaking about graphing two values on a point graph, mathematicians have agreed that the order should always be the same, hence the name ordered pair. The distance represented on the horizontal axis (x) always comes first, before the distance represented on the vertical axis (y). In this way, there is no ambiguity as to where the data point is. For example, the ordered pair (5,2) refers to one and only one possible point—the point which is 5 units to the right of zero on the horizontal axis and 2 units vertical. The ordered pair (2,5) refers to an entirely different point on the graph. See the graph below.

The standard convention further directs that in an ordered pair, the two numbers are separated by a comma and displayed in parentheses.

Student Guide:
Student Activity Book:
Master: