In the Key to Metric Measurement series, students learn how to measure in metric units-- - the only system used in international commerce and communication, and most commonly used in science and technical fields. Students who learn to use the metric system early will be more comfortable as adults with this form of measurement. Includes: Key to Metric Measurement Book 1: Metric Units of Length Key to Metric Measurement Book 2: Measuring Length and Perimeter Using Metric Units Key to Metric Measurement Book 3: Finding Area and Volume using Metric Units Key to Metric Measurement Book 4: Metric Units for Mass, Capacity, Temperatures, and Time.