## Measurement: Tips and Tricks

• Discuss with students why there is a need for standard units of measure. Have them research ancient measurement systems that were based upon nonstandard units, such as the size of a person's hand or foot. Discuss how using such units would lead to inaccurate measurements.
• After teaching Lesson 1, discuss with students the concept that measurements made by direct comparison are not exact. Students should realize that measuring is done to a unit of precision and that measuring the same object multiple times or having many people measure the same object may produce slightlydifferent results.
• Have students find the perimeter of a variety of objects in the classroom, including their textbooks, floor tiles, and desktops.
• Have students measure the same object in different ways. For example, have them measure the perimeter of one side of a fish tank in feet and inches and then in centimeters and millimeters. Have them pour water into the fish tank to measure its capacity in both gallons and liters. If possible, have them weigh the tank in pounds and find its mass in kilograms.
• Use familiar referents for standard unitsso that students will be able to estimate length, weight, and capacity. For example, a baseball bat is about 1 meter in length and 1 kilogram in mass. Your pinkie finger is about 1 centimeter wide. A dime is about 1 millimeter thick. A football weighs about 1 pound, and a large paper clip or thumbtack has a mass of about 1 gram. Have students measure the length or width of their hands in centimeters and inches to help them estimate linear measurements.
• If students have difficulty with converting between customary units of capacity, provide them with cup, pint, quart, and gallon measures. Have them pour water from one measure to another to explore how these capacities are related.
• You may wish to challenge the class by showing the students a diagram like the one below. Explain that each unit in the metric system is 10 times the size of the unit to its right. When converting a larger unit to a smaller unit, multiply. Note that the tables include hectometers (hm) and dekameters (dam), which are units that students will learn about in Grade 4.  3 0 0 0 0 0 0 km hm dam m dm cm mm
 3 km = 30 hm 3 km = 300 dam 3 km = 3,000 m 3 km = 30,000 dm 3 km = 300,000 cm 3 km = 3,000,000 mm

When converting a smaller unit to a larger unit, divide.

 3,000,000 mm = 300,000 cm 3,000,000 mm = 30,000 dm 3,000,000 mm = 3,000 m 3,000,000 mm = 300 dam 3,000,000 mm = 30 hm 3,000,000 mm = 3 km
• Using a newspaper or weather reports, make a chart of the daily high and low temperatures in both Fahrenheit and Celsius for one week. Have students find the difference between the highs and lows on the same day as well as on different days.
• To help students understand the Celsius temperature scale, teach them this rhyme: Thirty is hot, Twenty is nice, Ten is chilly, Zero is ice.
• Once students understand both the customary and metric systems, relate customary units to metric units. One inch is about 2 centimeters. One yard is a little less than 1 meter. One liter is a little more than 1 quart. One kilogram is a little more than 2 pounds. One kilometer is a little more than mile.
• Have students bring in examples of products that are labeled in both metric and customary units. For example, on most food packages, the weight is given in both customary and metric units, whereas the nutritional information is given in metric units.
• Have students discuss the differences between the metric systems and the customary system. Have them write an essay giving their opinion on which system is easier to use and whether or not the U.S. should convert to the metric system.