To begin the lesson, read How Big Is a Foot? to students. This amusing story tells of a king who wants to have a bed made just the right size for his queen. He measures her width and length with his king-size feet. The job of building the bed falls to a little apprentice who carefully uses the king's dimensions, but uses his little feet as the unit. Students enjoy explaining why the bed turns out to be too small for the queen and posing solutions to the dilemma.
Explain to the students that, although this is a fictional story, it is based upon fact. Our standard unit of measure, the foot, actually did come from making a model of a king's foot; and the standardized tool became known as a "ruler." Show a ruler so students can imagine a king's foot.
Have each student trace around his or her shoe on construction paper and cut out about six of these paper feet. Tape them heel to toe. Let the students use this new "six-foot" measure to find and record the length of common objects around the room.
After about ten minutes, lead the class in a discussion, comparing their measurements. Chart the data to use as a visual reference. Ask questions that help students compare their findings, for example:
- Who measured the height of the desk? What did you find?
- Who found a different measurement for the height of the desk?
- Why do you think it was different from ____'s?
- Is the desk really taller for ____ than for ____?
Show the students a variety of rulers (wooden, plastic, metal). Ask, does anyone have an idea about why we use rulers instead of paper feet taped together? Enjoy the idea-sharing! Note levels of thinking, reasoning, and creativity.
Then, explain that inches began in medieval England and were based upon the width of the human thumb. Thumbs were excellent measuring tools because even the poorest individuals had them available when they went to market.
Ask students to draw, along the edge of their construction paper, a line equal to the width of their thumbs. Cut the edge off the paper (about an inch wide), and accordion-fold the strip to show 12 student "inches."
Have students compare the length of their 12 inches to the tracing of their shoes. Share observations. (Note: 12 student inches should be about the same as 1 student foot.) Explain that body measurements were probably the most convenient references for length measurement long ago.
Distribute the Body Parts activity sheet. Define, model, and have students repeat each of the body measurements on the chart.
With partners, have students measure and record the lengths of their own digits, hands, cubits, yards, and fathoms.
After about ten minutes, call students together to discuss the term "cubit." The cubit was devised by the Egyptians about 3000 BC, and is generally regarded as the most important length standard in the ancient Mediterranean world. The Egyptians realized that a standardized cubit was necessary in order for measurements to be fair, so a master "royal cubit" was made of black granite. The present system of comparing units of measure with a standard physical tool (such as a ruler or yardstick) follows directly from this Egyptian custom.
Ask for a volunteer and attempt to measure his or her height using your forearm (cubit). Ask for solutions to the difficulty and awkwardness. [One solution should be to make a model that is the length of your own cubit.] Direct students to make a model of their cubits using either string, ribbon, adding machine tape, or interlocking cubes. Have partners check for accuracy.
Have students duplicate their cubit models and use them to estimate, measure, and record the height of several classmates. At the end of the activity (about ten minutes), have students share ideas of which models worked best for measuring height.
