436 CHAPTER 7 The Metric System Group Activities In Exercises 65– 68, (a) estimate the mass of the item and (b) if a scale with metric measure is available, determine the mass. 65. Your cell phone Answers will vary 66. A watermelon Answers will vary 67. A case of bottled water Answers will vary 68. Your shoes Answers will vary Challenge Problems In Example 2, we showed how to determine the volume and mass of water in a fish tank. Exercises 69 and 70 demonstrate how much more complicated solving a similar problem is in the U.S. customary system. 69. Fish Tank A rectangular fish tank is 1 yd long by 1.5 ft high by 15 in. wide. a) Determine the volume of water in the fish tank in cubic feet. 5.625 ft3 b) Determine the weight of the water in pounds. One cubic foot of water weighs 62.48 lb. 351.45 lb c) One gal of water weighs 8.34 lb. How many gallons will the tank hold? Round to the nearest hundredth. 42.14 gal 70. Restaurant Fish Tank The rectangular fish tank at Anna Maria Oyster Bar is 2 yd long by 2.5 ft high by 24 in. wide. a) Determine the volume of water in the fish tank in cubic feet. 30 ft3 b) Determine the weight of the water in pounds. One cubic foot of water weighs 62.48 lb. 1874.4 lb c) One gal of water weighs 8.34 lb. How many gallons will the tank hold? Round your answer to the nearest hundredth. 224.75 lb Recreational Mathematics 71. Balance the Scale Determine the quantity needed to replace the question mark to make the scale balance. The weight times the distance on both sides of the fulcrum (the triangle) must be the same to make the scale balance. 1500 g ? g 2 m 400 cm 3 kg 72. Interesting Facts According to Weather.com, a) The lowest temperature ever recorded in the United States was 62.11°C − on January 23, 1971, in Prospect Creek, Alaska. What is this temperature in degrees Fahrenheit? 79.8°F ≈− b) International Falls, Minnesota, has the lowest annual mean (average) temperature in the United States (including Alaska). Its mean annual temperature is about 2.5°C. What is this temperature in degrees Fahrenheit? 36.5°F Research Activity 73. The Kilogram Write a report on the history and the use of the kilogram. Be sure to include the discussion of Le Grand K and its historical role in the metric system. In this section, we will use a process called dimensional analysis to convert units of measurement from the U.S. customary system to the metric system, and vice versa. Dimensional analysis is used in many fields of science, especially chemistry and physics. It can also be used to convert units of measurement in many other areas. For example, a medicine dosage given in milligrams per kilogram of a patient may need to be converted to ounces per pound of the patient. While traveling outside the U.S., you may need to know how to convert a speed limit given in kilometers per hour to miles per hour. You may also need to know how to convert among various currencies while traveling. Dimensional Analysis and Conversions to and from the Metric System SECTION 7.4 LEARNING GOALS Upon completion of this section, you will be able to: 7 Understand dimensional analysis. 7 Make conversions to and from the metric system. Mark Adams/123RF
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