Lesson 12: Estimate and Add

Estimate and Add

10 min

Narrative

The purpose of this Number Talk is for students to develop strategies for adding decimals with a focus on composing a new whole number. Students will work on sums where a new whole number is composed throughout the lesson.

Launch

Display one expression.
“Give me a signal when you have an answer and can explain how you got it.”

Teacher Instructions

1 minute: quiet think time
Record answers and strategy.
Keep expressions and work displayed.
Repeat with each expression.

Student Task

Find the value of each expression mentally.

$1.00 + 0.99 + 0.02$
$1.99 + 0.02$
$1.99 + 0.03$
$1.99 + 0.13$

Sample Response

2.01: I added one of the hundredths from 0.02 to 0.99 to make another whole and then I had 2 and one hundredth.
2.01: It is the same problem as the first one, but $1.00 + 0.99$ is written as 1.99.
2.02: It is 1 hundredth more than the last one.
2.12: It is 1 tenth more than the last one and $2.02 + .1 = 2.12$ .

Activity Synthesis (Teacher Notes)

“How did you use the value of one of the expressions to help you find the value of a different expression?” (I knew that $1.99 + 0.13$ is 0.1 more than $1.99 + 0.03$ .)

Standards

Addressing

5.NBT.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
5.NBT.B.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

15 min

20 min

Knowledge Components

All skills for this lesson

No KCs tagged for this lesson

Estimate and Add

10 min

Narrative

Launch

Display one expression.
“Give me a signal when you have an answer and can explain how you got it.”

Teacher Instructions

1 minute: quiet think time
Record answers and strategy.
Keep expressions and work displayed.
Repeat with each expression.

Student Task

Find the value of each expression mentally.

$1.00 + 0.99 + 0.02$
$1.99 + 0.02$
$1.99 + 0.03$
$1.99 + 0.13$

Sample Response

2.01: I added one of the hundredths from 0.02 to 0.99 to make another whole and then I had 2 and one hundredth.
2.01: It is the same problem as the first one, but $1.00 + 0.99$ is written as 1.99.
2.02: It is 1 hundredth more than the last one.
2.12: It is 1 tenth more than the last one and $2.02 + .1 = 2.12$ .

Activity Synthesis (Teacher Notes)

“How did you use the value of one of the expressions to help you find the value of a different expression?” (I knew that $1.99 + 0.13$ is 0.1 more than $1.99 + 0.03$ .)

Standards

Addressing

5.NBT.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
5.NBT.B.7·Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.

Estimate and Add

Warm-up Number Talk: 99 Hundredths 10 minKCs

Narrative

Launch

Student Task

Sample Response

Activity Use the Standard Algorithm to Add Decimals 15 minKCs

ActivityEstimate and Find the Value 20 minKCs

Knowledge Components

Estimate and Add

Warm-up Number Talk: 99 Hundredths 10 minKCs

Narrative

Launch

Student Task

Sample Response

Activity Use the Standard Algorithm to Add Decimals 15 minKCs

ActivityEstimate and Find the Value 20 minKCs

10 min

15 min

20 min

10 min

15 min

20 min