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Weight and Capacity

Measurements

Grade 4: Unit 5: Lesson 14

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Lesson Purpose

The purpose of this lesson is for students to apply their understanding of multiplicative comparison

and unit conversion to solve multi-step problems about weight and capacity.

Lesson Narrative

In earlier lessons, students were introduced to several units of weight and capacity (kilograms,

grams, pounds, ounces, liters, and milliliters). In this lesson, students solve problems involving the

units of capacity they worked with in grade 3. They use their knowledge of unit conversion and

multiplicative reasoning to solve multi-step problems. Students may need to review the

measurement units used in this lesson before the lesson to ensure access to the tasks.

Learning Goals

• Use multiplicative comparison and unit conversion to solve multi-step problems about weight

and capacity (in pounds, ounces, gallons, quarts, and cups).

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Let’s solve problems about weight and capacity.

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Number Talk: Lots of Thousands

Warm-Up

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Find the value of each expression mentally.

1,200 + 900 =
12,500 + 9,000 =
13,000 + 9,900 =
130,000 + 99,000 =

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Let’s Talk About It!

How was finding the first sum like finding the last sum?

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Milk and Mango Lassi

Activity 1

MLR8: Discussion Supports

In this activity, students work with customary units of capacity for liquids (gallon, quart, and cup).

The task prompts them to discern the relationship between the units, express the relationships with

multiplicative comparison statements, and perform conversions to solve problems. When

they identify the relationship between gallons, quarts, and cups students reason abstractly and

quantitatively (MP2).

To compare quantities given in different units, students choose which unit to use for comparison

and consider the implications of their choice. Students are likely to convert a value in a larger unit

to to a smaller unit (from gallons and quarts to cups), but some may reason the other way around

(from cups and quarts to gallons, ending up with fractional amounts). In grade 4, students are

expected only to convert from a larger unit to a smaller one.

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Here are three true statements about this jug of milk.

• This jug contains 1 gallon of milk.

• This jug contains 4 quarts of milk.

• This jug contains 16 cups of milk.

Complete each statement so that it is true:

a. One gallon is ______ times as much as 1 quart.

b. One gallon is______ times as much as 1 cup.

c. One quart is______ times as much as 1 cup.

Launch

• Groups of 2

• Read the first sentence and the bullet points in the first problem.

• Display a one-gallon jug (with or without milk), a one-quart container, and a one-cup

container. Tell students that, when filled up, the jug holds 1 gallon.

• “Here is a container that holds 1 quart of liquid. How is that amount related to the amount in

the jug?” (It takes 4 of these to fill up the jug.)

• “Here is a container that holds 16 cups. How is that amount related to the amount in the jug?”

(It takes 16 of these to fill up the jug.)

• “Complete the statements in the first problem. Then, share your responses with your partner.“

• 1 minute: quiet think time

• 1 minute: partner discussion

• “Let’s use what we know about these units for measuring liquids to solve some problems.”

• Explain to students

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For a potluck party, Priya and three other

relatives are bringing mango lassi.

a. Who prepared the most mango lassi? Explain or show your reasoning.

b. How many cups of lassi did all the guests bring?

c. Complete this sentence: Priya’s grandma___________ made times as much lassi as Priya’s cousin. Show how you know.

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Let’s Talk About It!

How does the diagram show that 1 gallon is 4 times as much as 1 quart and 16 times as much as 1 cup?

Activity Synthesis

• Poll the class on the unit they used to compare the amounts of lassi.

• Select a student who chose each option to share the rationale behind their decision.

• Display the table with an extra column for showing the amounts in cups.

• Invite students to share their responses to the questions about lassi and their reasoning,

completing the table along the way.

• Highlight that converting the amounts into the same unit helped us: see the greatest amount,

find the total amount, and see how many times as much lassi one guest made compared to

another guest.

• To reinforce students’ understanding of the relationship between the units of capacity used

here, consider creating a diagram such as shown.

• “How does the diagram show that 1 gallon is 4 times as much as 1 quart and 16 times as

much as 1 cup?”

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Clay for Art Class

Activity 2

MLR6: Three Reads

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Have you used clay to make an object or build a figure?

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At a craft store, clay is sold in packs of different sizes: 1 pound, 24 ounces, 3 pounds, and 5 pounds.

An art teacher needs 120 ounces of clay for her class.

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Would she have enough clay if she bought each of the following combinations? Explain or show your reasoning.

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Decide if each statement is true or false. Be prepared to explain or show your reasoning.

a. A 3-pound pack weighs 2 times as much as a 24-ounce pack.

b. If we combine a 1-pound pack, a 3-pound pack, and a 5-pound pack, we’d have 6 times as much clay as what’s in a 24-ounce pack.

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Let’s Talk About It!

Did anyone reach the same conclusion but reasoned in a different way?

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Lesson Synthesis

If someone claimed that 3 quarts is greater than 2 gallons because 3 is greater than 2, how would you explain that this is not true? What correction would you offer?

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More Clay

Cool-Down

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An art teacher and a kindergarten teacher are getting clay from the craft store. The art teacher buys 6 pounds of clay. This amount is 4 times as much clay as what the kindergarten teacher buys.

How many ounces of clay do the two teachers buy all together? Explain or show your reasoning.

Cool-Down: More Clay

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Image Citations

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