Mathematics
Grade 7
15 min
Which customary unit of weight is appropriate?
Which customary unit of weight is appropriate?
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Introduction & Learning Objectives
Learning Objectives
Identify the three main customary units of weight: ounce, pound, and ton.
Describe the approximate weight represented by an ounce, a pound, and a ton.
Select the most appropriate customary unit of weight for various real-world objects.
Explain the relationships between ounces, pounds, and tons using conversion factors.
Justify the choice of a customary unit of weight based on the object's estimated mass.
Solve problems involving the selection of appropriate customary units of weight.
Ever wondered if you'd weigh a feather in tons or a truck in ounces? 🤔 Choosing the right unit makes all the difference!
In this lesson, you'll learn about the customary units of weight—ounces, pounds, and tons—and how to decide which one is best for measurin...
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Key Concepts & Vocabulary
TermDefinitionExample
WeightThe measure of how heavy an object is, determined by the force of gravity acting on its mass.A rock has more weight than a feather because it is heavier.
Customary Units of WeightThe system of measurement for weight commonly used in the United States.Ounces, pounds, and tons are the primary customary units of weight.
Ounce (oz)A small customary unit of weight, typically used for very light objects.A slice of bread, a letter, or a small candy bar weighs a few ounces.
Pound (lb)A customary unit of weight larger than an ounce, commonly used for everyday objects.A loaf of bread, a bag of apples, or a small pet weighs a few pounds.
Ton (T)A very large customary unit of weight, used for extremely heavy objects.A car, an elephant, or a small truck weighs several tons....
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Core Formulas
Ounce to Pound Conversion
$1 \text{ pound (lb)} = 16 \text{ ounces (oz)}$
Use this rule to convert a weight from ounces to pounds or vice-versa. It shows that 16 ounces are equivalent to 1 pound.
Pound to Ton Conversion
$1 \text{ ton (T)} = 2000 \text{ pounds (lb)}$
Use this rule to convert a weight from pounds to tons or vice-versa. It shows that 2000 pounds are equivalent to 1 ton.
Unit Appropriateness Guideline
Use **ounces** for very light objects. Use **pounds** for medium-weight objects. Use **tons** for very heavy objects.
This guideline helps you select the most practical and understandable unit for measuring an object's weight, aiming for numbers that are easy to comprehend.
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Challenging
Imagine a new customary unit of weight called a 'stone' is equal to 14 pounds. For which of the following would 'stones' be the most appropriate unit of measurement?
A.car (approx. 4,000 lbs)
B.human adult (approx. 140 lbs)
C.laptop (approx. 4 lbs)
D.blue whale (approx. 300,000 lbs)
Challenging
A city bus has a weight limit of 15 tons. It can carry 50 passengers. If the average passenger with their belongings weighs 180 pounds, what is the most appropriate unit to express the total weight of a full load of passengers, and what is that approximate weight?
A.Ounces, because it is the most precise unit; 144,000 oz
B.Pounds, because it is the unit used for the initial calculation; 9,000 lbs
C.Tons, because it allows for easy comparison to the bus's limit; 4.5 T
D.Tons, because passengers are very heavy; 9 T
Challenging
A student correctly calculates that a 4-ton elephant weighs 128,000 ounces. They argue that because the number is so large and impractical, the conversion itself is an inappropriate use of mathematics. What is the flaw in this student's argument?
A.The student's calculation is wrong; 4 tons is not 128,000 ounces.
B.The student is correct; you should never convert between tons and ounces.
C.The math is correct, but the flaw is in the student's conclusion. The calculation is valid, but it demonstrates *why* ounces are an inappropriate *unit choice* for an elephant, not that the math is inappropriate.
D.The flaw is that pounds should have been the final unit, not ounces.
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