lesson 25 objective: divide a whole number by a unit fraction by the end of the lesson, i will be...

LESSON 25OBJECTIVE: DIVIDE A WHOLE NUMBER BY A UNIT FRACTION

By the end of the lesson, I will be able to…

5TH GRADE MODULE 4– LESSON 25K. CLAUSON

WRITE FRACTIONS AS DECIMALS

MULTIPLY FRACTIONS BY DECIMALS

APPLICATION PROBLEM

The label on a 0.118 L bottle of cough syrup recommends a dose of 10 mL for children aged 6 to 10 years. How many 10 mL doses are in the bottle?

PROBLEM 1Jenny buys 2 pounds of pecans. a. If Jenny puts 2 pounds in each bag, how many bags can she make?

Work with your partner to write a division sentence that explains your thinking.

How many bags of pecans can she make?

Concept Development

2 ÷ 2 = 1

1 bag

PROBLEM 1Jenny buys 2 pounds of pecans. b. If she puts 1 pound in each bag, how many bags can she make?

Write a division sentence for this situation and solve.

Answer the question in a complete sentence.

Concept Development

2 ÷ 1 = 2

She can make 2 bags.

PROBLEM 1Jenny buys 2 pounds of pecans. c. If she puts 1/2 pound in each bag, how many bags can she make?

What would this division sentence look like?

Will the answer be more or less than 2?Let’s use a rectangular piece of paper to show this!

Concept Development

2 ÷ ½ = 2* It is like asking how many halves are in 2.

PROBLEM 1Jenny buys 2 pounds of pecans. c. If she puts 1/2 pound in each bag, how many bags can she make?

Let me model this with a tape diagram and a number line.

Concept Development

PROBLEM 1 There are 4 halves in 2

wholes. She can make 4 bags. But how can we be sure 4 halves is correct? How do we check a division problem? By what do we need to multiply the quotient?

What is the quotient? What is the divisor?

What would our checking expression be?

4 x ½ = 2

PROBLEM 1Jenny buys 2 pounds of pecans. d. If she puts 1/3 pound in each bag, how many bags can she make?

Concept Development

(model with paper rectangle first)

PROBLEM 1Jenny buys 2 pounds of pecans. e. If she puts 1/4 pound in each bag, how many bags can she make?

Concept Development

JENNY’S PROBLEMS SHOW US SOME PATTERNS! CAN YOU SEE THEM?!?

2 ÷ 2 = 1 2 ÷ 1 = 2 2 ÷ ½ = 4 2 ÷ ⅓ = 6 2 ÷ ¼ = 8

Do you notice…? We start with 2 pounds each time, but then it is being divided by a smaller and smaller unit.The answer is getting larger and larger.

When the 2 pounds is divided into smaller units, then the answer is bigger.

WHY?????

When we cut a whole into smaller parts, then we’ll get more parts.

The more units we split from one whole, then the more parts we’ll have. That’s why the quotient is becoming larger.

PROBLEM 2Jenny buys 2 pounds of pecans. a. If this is 1/2 the number she needs to make pecan pies, how many pounds will she need?

Two is half of what number?

Give me the division sentence. (Be careful!)

2 x 2 = 4 OR ½ x 4 = 2

PROBLEM 2Let’s try to write a division expression for this whole number situation…. 4 x ____ = 8What would the complete division sentence be?

8 ÷ 4 = 2

Now try the same process with ½ x ___ = 2Give me the division expression with the answer. 2 ÷ ½ = 4

PROBLEM 2Jenny buys 2 pounds of pecans. a. If this is 1/2 the number she needs to make pecan pies, how many pounds will she need?

What is the whole unit in this story?

PROBLEM 2Jenny buys 2 pounds of pecans. b. If this is 1/3 the number she needs to make pecan pies, how many pounds will she need?

PROBLEM 2Jenny buys 2 pounds of pecans. c. If this is 1/4 the number she needs to make pecan pies, how many pounds will she need?

Skip this maybe?!

PROBLEM 3

Tien wants to cut ¼ foot lengths from a board that is 5 feet long. How many boards can he cut?

GET READY TO FINISH THEPROBLEM SET ON YOUR OWN!

Work on Problem Set 25.You will have 10 minutes to work!

-------------------------------------------------------------------Fast finishers: Math Center Activities- choice boards,

extra Sprint challenge CML packets/ worksheets Problem Solving pages 5TH GRADE MODULE 4– LESSON 25

K. CLAUSON

5TH GRADE MODULE 4- LESSON 25K. CLAUSON

LET’S DEBRIEF

• Take 2 minutes to check your answers with your partner.

• Let’s share any insights you had while solving these problems.

5TH GRADE MODULE 4– LESSON 25K. CLAUSON

EXITTICKETLESSON 25