Hand Span Measures

Task

Hand span is a measure of distance from the tip of the thumb to the tip of the little finger with the hand fully extended.

• Each student places his or her dominant hand on the edge of a piece of paper with the hand fully extended.
• The student should make a mark at the tip of the thumb and the tip of the little finger. The distance between marks is the length of the hand span.
• The student should measure his or her hand span with a centimeter ruler and round the measurement to the nearest whole centimeter.
• Each student should record his or her measurement on a piece of paper.

The teacher can ask each student for his or her measurement and record the data using a line plot with a horizontal scale marked off in whole centimeters. Alternatively, the teacher can set up the line plot and ask each student to come record his or her own hand span, showing the students how by recording the teacher's hand span.

Students should comment about patterns they observe the line plot and write or discuss the answers to these two questions:

1. What are the largest and smallest spans? What is the difference between the largest and smallest spans?

2. Use words to describe the shape of the data set. Does it appear taller in the center like a mountain? Are there peaks in more than one place? Is the shape of the data flat like a table top? Are there gaps? Are some hand spans much bigger or smaller than the others?

IM Commentary

The size of the hand makes a difference in some sports that involve throwing or catching and some activities such as playing the piano. Hand span is a measure that has been used for many years.

By placing the hand on the edge of a piece of paper and marking the tips of the thumb and little finger, the student can measure a straight line. This is a better method than placing the hand directly on the ruler. Discuss rounding conventions. This could be used as a class activity, or students could gather and plot data on separate line plots from different age groups.

Submitted by Miriam L. Clifford for Illustrative Mathematics Task Writing Contest Jan 17 - Jan 30, 2012

Solution

Students from ages 6 – 12 usually have a span in the range of 15 to 20 cm, with an average of about 17 cm. The teacher or students should record class data by placing an X above the appropriate number on the horizontal scale for each hand span that is measured. Or, provide a square post-it note to each student. Each student records his or her hand span on the note and posts it directly above the appropriate number on the horizontal line plot. The scale on the graph should match the size of the post-it notes. Post-it notes should be placed edge-to-edge and should not overlap.

Here is data from Jackie Giacalone's 2nd grade classes at Waukesha STEM Academy – Randall Campus in Waukesha, WI:

1. The difference between the largest and smallest measures is the range. This number is helpful in describing the “spread” of the data.

2. Encourage students to think of the data as a collection of points that form a shape or picture. They should use their own words to describe the shape and any interesting features of the data set.