Lesson 2-1 Mental Math

Lesson 2-1 Mental Math

5th Grade Math

Open Ended

On a scale of Avengers, how do you feel today? 

​Agenda

1) Solve & Share ​

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​2) Key Vocabulary (commutative property, associative property, compatible numbers, and compensation)

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​3) Convince Me ! for checking on your understanding

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​4) Guided Practice working in groups

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​5) Independent Practice working in groups

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​6) Practice Buddy working independently

Open Ended

What is the total cost of the software? Use mental math to solve.

Solve the problem on page 45 and on this quizizz. 

​Tara's work - 2-1 Solve and Share

• ​Three pieces of software cost $20.75, $10.59, and $18.25. What is the total cost of the software? Use mental math to solve.

​Kyle's work - 2-1 Solve and Share

• ​Three pieces of software cost $20.75, $10.59, and $18.25. What is the total cost of the software? Use mental math to solve.

Objective ​

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I can use mental math to solve addition and subtraction problems. 

​Essential Question

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How can we manipulate numbers to help us solve problems using mental math?

Open Ended

Explain how you can find the sum to $4.75 ​+ $1.50 + $1.25, mentally. 

​Explain how you can find the sum to $4.75 ​+ $1.50 + $1.25, mentally. 

​You can use the commutative property to rearrange the addends, so $4.75 + $1.25 + $1.50 will be the new order of the numbers. I can add $0.75 + $0.25 which is $1. Now, $4 + $1 + $1 = $6. Finally, $6 + $1.50 = $7.50.

​Key Vocabulary - take notes

Commutative property - focus on the order of numbers does not matter

​$11.45 + $ 3. 39 = $3.39 + $11.45 Think : movement or commuting

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​Associative property - focus on the groupings of numbers does not matter

​($11.45 + $3.39) + $9.55 = $11.45 + ($3.39 + $9.55) Think: associating yourself with a group

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​Compatible number - numbers that are easy to calculate mentally

​$11.45 + $9.55 = $21 and $21 + $3.39 = $24.39

​Key Vocabulary - take notes

​Questions?

Multiple Choice

Can you always use the commutative property with subtraction?

• YES

• NO

Open Ended

Give one example as to why using the commutative property does not work with subtraction.

Open Ended

In your own words, explain the associative property. 

Mental math ​helps us solve problems faster, but there are multiple ways you can use mental math

Open Ended

How much did he earn in all? Use mental math to find the sum. Explain your thinking. 

Solve the problem on page 46 and on this quizizz.  

​2-1 Convince Me! page 46

Open Ended

GROUPS: Solve the problem on the Guided Practice problem of page 47 and on this quizizz. 

Open Ended

GROUPS: Solve the problem on the Guided Practice problem of page 47 and on this quizizz. 

Open Ended

GROUPS: Solve the problem on the Guided Practice problem of page 47 and on this quizizz. 

Open Ended

GROUPS: Solve the problem on the Independent Practice problem of page 47 and on this quizizz. 

Open Ended

GROUPS: Solve the problem on the Independent Practice problem of page 47 and on this quizizz. 

​Independent Work

​Complete the 2-1 Practice Buddy. You will work for the remaining time in class. When done, work on Prodigy.