Have you ever studied animals? Julie has been learning about certain ones in the rainforest.
Julie has decided that her favorite rainforest topic has to do with the animals. She reads that the red-eyed tree frog weighs about 15 ounces while an male adult gorilla usually weighs 450 pounds. Julie begins writing down facts about each animal in her journal. She isn’t sure which facts she’ll use in her final report, but she is fascinated with all of the different types of animal species that are found in the rainforest. While she is working, her teacher Mr. Gibbons asks her how it is going. Julie begins to tell him about the gorilla and the tree frog.
“Wow,” Mr. Gibbons says. “I wonder how many tree frogs it would take to equal the weight of one gorilla, or how many 90 pound girls it would take?”
“I don’t know,” says Julie beginning to think about all of the numbers in her mind.
“Sounds like a problem worth investigating to me,” Mr. Gibbons smiles as he walks away. Julie begins by drawing a picture of a balance scale. On one side she draws a gorilla and on the other side she draws a tree frog. Then Julie begins her calculations.
You will need information about weight and about the customary units of measurement to figure out this problem. This Concept will teach you all that you need to know.
You have already learned about measuring length using the customary system of measurement. Remember that the customary system of measurement is used in the United States and it contains units like inches, feet, yards and miles. The metric system is the other system of measurement that is used in science and in many other countries. This Concept will focus on customary units of weight and volume. Let’s begin by looking at the customary units of weight.
What are the customary units of weight?
First, what do we mean when we talk about weight? We mean the heaviness or the way a mass of something or someone feels due to gravity. The customary units for measuring weight are ounces, pounds and tons.
An ounce is the smallest common unit of weight, a pound is what we commonly use for measuring medium sized objects and a ton is what we use to measure very large objects.
What about equivalence?
Remember, when we see the word equivalent we are referring to something being equal to something else. When working with measures of weight, we can compare the equivalence of a small unit to a larger one. Here are the customary units of equivalence.
Here are the units from smallest to largest.
We can find equivalent measures for each unit by using the information in each arrow. We can convert from a larger unit to a smaller unit by multiplying. We can convert from a smaller unit to a larger unit by dividing.
How many ounces are 3 pounds of stones?
To solve this problem, we need to convert pounds to ounces. A pound is larger than an ounce, so we are going to multiply. There are 16 ounces in one pound. We can multiply the number of pounds times 16 and this will give us the total number of ounces.
16 × 3 = 48
Our answer is 48 ounces.
We can also convert a smaller unit to a larger unit. To do this, we would divide.
How many tons is 6200 pounds?
To solve this problem, we are going to divide. There are 2000 pounds in one ton, so we are going to divide 6200 pounds by 2000 to get our answer in tons.
6200 ÷ 2000 = 3.1 tons
You can also write your answer in different forms. You could write it as a fraction, a decimal or with a remainder.
Problem: 100 ounces = ____ lb?
We solve this by dividing 100 by 16, since there are 16 ounces in one pound.
Fractional answer: 100÷16=6416=614 lb
Decimal answer: 100÷16=6416=6.25 lb
Remainder answer: 100÷16=6 R 4=6 lb 4 oz
Now it's time for you to try a few of these on your own. Convert the following units of weight. You may write your answer as a fraction or a decimal when necessary.
5 tons = ____ pounds
Solution: 10,000 pounds
32 ounces = ____ pounds
Solution: 2 pounds
4500 pounds = ____ tons
Solution: 2.25 tons
Now let's think about those animal weights.
First, it is time to answer the two questions. The first one is how many tree frogs will it take to equal the weight of one gorilla.
Julie begins by converting pounds to ounces.
450 pounds (Gorilla) = ____ ounces
To solve this, we multiply 450 by 16 since there are 16 ounces in one pound.
450 pounds = 7200 ounces.
Next, the tree frog weighs 15 ounces. Julie divides 7200 by 15. She gets an answer of 480.
It will take 480 tree frogs to equal the weight of one gorilla.
The second question is the one that Mr. Gibbons asked Julie. “How many 90 pound girls is equal to one gorilla?” Julie divides 450 by 90.
450 ÷ 90 = 5
It takes five 90 pound girls to equal one gorilla.
Here are the vocabulary words in this Concept.
measurement of the heaviness or mass of someone or something
the smallest common unit of weight in the customary system, used to measure very small items.
the most common unit for measuring weight, most things are measured in pounds.
the largest common unit for measuring weight-very large items are measured by the ton-for example, a car or truck.
Here is one for you to try on your own.
A male African elephant usually weighs between 6 and 8 tons. If this the range of his weight in tons, what is the range of his weight in pounds?
To figure this out, we must first think about the equivalent measure between tons and pounds.
2000 pounds = 1 ton
Given this equivalent, the range of weight is between 12,000 and 16,000 pounds.
This is our answer.
Here is a video for review.
Khan Academy US Customary and Metric Units
Directions: Convert each customary unit of weight to an equivalent form.
1. 32 ounces = ____ pounds
2. 6 pounds = ____ ounces
3. 5.5 pounds = ____ ounces
4. 60 ounces = ____ pounds
5. 9 pounds = ____ ounces
6. 4000 pounds = ____ tons
7. 4 tons = ____ pounds
8. 3.5 tons = ____ pounds
9. 6500 pounds = ____ tons
10. 7.25 tons = ____ pounds
11. 15 pounds = ____ ounces
12. 25 tons = _____ pounds
13. 64 ounces = ____pounds
14. 80 ounces = ____ pounds
15. 5 tons = _____ pounds