Session 3, Part B:
Metric Units (85 minutes)

In This Part: Length | Liquid Volume | Mass | Reasoning With Balance Scales

 As we've seen, the base unit for length (or distance) is the meter. Meter comes from the Greek word "metron," which means "measure." Many of us do not have a strong intuitive sense of metric lengths, which may be a result in part of our limited experience with metric measures and estimates. It is, however, important to have referents for measures, as referents make measurement tasks easier to interpret and provide us with benchmarks against which to test the reasonableness of our measures. Note 5 Problem B1 Print this centimeter grid (PDF - be sure to print this document full scale) and paste it onto stiff cardboard paper. Cut and tape pieces together to build a meterstick, and explore how you would mark decimeters, centimeters, and millimeters on it.

Problem B2

a.

Find a friend or colleague, and use a metric tape measure to measure the following body lengths: A, B, C, D, and E (as pictured below). Your goal is to try to find your own personal referents for 1 cm, 1 dm, and 1 m.

b.

Using the information you gathered, estimate these lengths:

 • The height of a door • The length of your table • The width of a notebook • The thickness of a dime • The length, width, and height of the room

Problem B3

 a. Approximate a distance of 100 m. First plan how you will determine this length, and then measure this distance outside. Mark off 100 m using chalk, and then use a trundle wheel to check your approximation. (A trundle wheel is a plastic wheel, usually graduated in 5 cm intervals, designed to measure lengths by counting the number of clicks, each of which equals 1m.) b. Use this distance to estimate the time it would take you to walk 1 km. If it's a nice day, check your estimate by actually walking 1 km. What is your average walking pace? Note 6

 Video Segment In this video segment, Mary and Susan work together to establish some referents for measuring lengths using their own bodies, for example, the width of a hand or an arm length. They use those referents to make measurements and then compare them to standard-unit measurements. Why is it important to establish such referents for measuring? Can you think of any situations in which they might be useful? If you are using a VCR, you can find this segment on the session video approximately 10 minutes after the Annenberg Media logo.

 Session 3: Index | Notes | Solutions | Video