Lesson 10: Writing and Expanding Multiplication

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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
6•4
Lesson 10: Writing and Expanding Multiplication Expressions
Student Outcomes
๏‚ง
Students identify parts of an expression using mathematical terms for multiplication. They view one or more
parts of an expression as a single entity.
Classwork
Discussion (4 minutes)
๏‚ง
When we want to show multiplication of two numbers, like 5 and 7, we typically write 5 × 7, using the “×” to
show the operation. When we start to use variables with multiplication, we can use other forms.
๐‘Ž×๐‘
๐‘Žโˆ™๐‘
๐‘Ž๐‘
(๐‘Ž)(๐‘)
๏‚ง
Why might we want to use a form other than the × when variables are involved?
๏ƒบ
๏‚ง
The × can be confused for a variable instead of a symbol for an operation.
Which of the three models can be used to show multiplication where there are no variables involved?
๏ƒบ
5 × 7, 5 โˆ™ 7, and (5)(7), but not 57 because it looks like the number fifty-seven and not five times
seven.
Example 1 (10 minutes)
MP.7
๏‚ง
When writing expressions using the fewest number of symbols, we have to refrain from using the symbols ×, โˆ™,
or ( ).
๏‚ง
We will also be using math terms to describe expressions and the parts of an expression. We will be using
words like factor, product, quotient, coefficient, and term.
๏‚ง
A term is a part of an expression that can be added to or subtracted from the rest of the expression. In the
expression 7๐‘” + 8โ„Ž + 3, what are examples of terms?
๏ƒบ
๏‚ง
7๐‘”, 8โ„Ž, and 3 are all terms.
A coefficient is a constant factor in a variable term. For example, in the term 4๐‘š, 4 is the coefficient, and it is
multiplied with ๐‘š.
Lesson 10:
Writing and Expanding Multiplication Expressions
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NYS COMMON CORE MATHEMATICS CURRICULUM
Lesson 10
6•4
Example 1
Write each expression using the fewest number of symbols and characters. Use math terms to describe the expressions
and parts of the expressions.
๐Ÿ”×๐’ƒ
a.
๐Ÿ”๐’ƒ; the ๐Ÿ” is the coefficient and a factor, and the ๐’ƒ is the variable and a factor. We can call ๐Ÿ”๐’ƒ the product,
and we can also call it a term.
๐Ÿ’โˆ™๐Ÿ‘โˆ™๐’‰
b.
๐Ÿ๐Ÿ๐’‰; the ๐Ÿ๐Ÿ is the coefficient and a factor, and the ๐’‰ is the variable and a factor. We can call ๐Ÿ๐Ÿ๐’‰ the
product, and we can also call it a term.
๐Ÿ×๐Ÿ×๐Ÿ×๐’‚×๐’ƒ
c.
๐Ÿ–๐’‚๐’ƒ; ๐Ÿ– is the coefficient and a factor, ๐’‚ and ๐’ƒ are both variables and factors, and ๐Ÿ–๐’‚๐’ƒ is the product and also
a term.
๏‚ง
Variables always follow the numbers and should be written in alphabetical order. Apply this knowledge to the
examples below.
๐Ÿ“×๐’Ž×๐Ÿ‘×๐’‘
d.
๐Ÿ๐Ÿ“๐’Ž๐’‘; ๐Ÿ๐Ÿ“ is the coefficient and factor, ๐’Ž and ๐’‘ are the variables and factors, ๐Ÿ๐Ÿ“๐’Ž๐’‘ is the product and also
a term.
MP.7
๏‚ง
If it is helpful, you can gather the numbers together and the variables together. You can do this because of the
commutative property of multiplication.
๏ƒบ
5×3×๐‘š×๐‘
๐Ÿ×๐’ˆ×๐’˜
e.
๐Ÿ๐’ˆ๐’˜ or ๐’ˆ๐’˜; ๐’ˆ and ๐’˜ are the variables and factors, ๐Ÿ is the coefficient and factor if it is included, and ๐’ˆ๐’˜ is
the product and also a term.
๏‚ง
What happens when you multiply by 1?
๏ƒบ
Multiplying by 1 is an example of the identity property. Any number times 1 is equal to that number.
Therefore, we don’t always need to write the one because 1 × ๐‘”๐‘ค = ๐‘”๐‘ค.
Example 2 (5 minutes)
Example 2
To expand multiplication expressions, we will rewrite the expressions by including the “ โˆ™ ” back into the expressions.
a.
๐Ÿ“๐’ˆ
๐Ÿ“โˆ™๐’ˆ
Lesson 10:
Writing and Expanding Multiplication Expressions
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NYS COMMON CORE MATHEMATICS CURRICULUM
b.
Lesson 10
6•4
๐Ÿ•๐’‚๐’ƒ๐’„
๐Ÿ•โˆ™๐’‚โˆ™๐’ƒโˆ™๐’„
c.
๐Ÿ๐Ÿ๐’ˆ
๐Ÿ๐Ÿ โˆ™ ๐’ˆ or ๐Ÿ โˆ™ ๐Ÿ โˆ™ ๐Ÿ‘ โˆ™ ๐’ˆ
d.
๐Ÿ‘๐’‰ โˆ™ ๐Ÿ–
๐Ÿ‘โˆ™๐’‰โˆ™๐Ÿ–
e.
๐Ÿ•๐’ˆ โˆ™ ๐Ÿ—๐’‰
๐Ÿ• โˆ™ ๐’ˆ โˆ™ ๐Ÿ— โˆ™ ๐’‰ or ๐Ÿ• โˆ™ ๐’ˆ โˆ™ ๐Ÿ‘ โˆ™ ๐Ÿ‘ โˆ™ ๐’‰
Example 3 (5 minutes)
Example 3
a.
๏‚ง
Find the product of ๐Ÿ’๐’‡ โˆ™ ๐Ÿ•๐’ˆ.
It may be easier to see how we will use the fewest number of symbols and characters by expanding the
expression first.
๐Ÿ’โˆ™๐’‡โˆ™๐Ÿ•โˆ™๐’ˆ
MP.7
๏‚ง
Now we can multiply the numbers and then multiply the variables.
๐Ÿ’โˆ™๐Ÿ•โˆ™๐’‡โˆ™๐’ˆ
๐Ÿ๐Ÿ–๐’‡๐’ˆ
b.
๏‚ง
Multiply ๐Ÿ‘๐’…๐’† โˆ™ ๐Ÿ—๐’š๐’›.
Let’s start again by expanding the expression. Then, we can rewrite the expression by multiplying the numbers
and then multiplying the variables.
๐Ÿ‘โˆ™๐’…โˆ™๐’†โˆ™๐Ÿ—โˆ™๐’šโˆ™๐’›
๐Ÿ‘โˆ™๐Ÿ—โˆ™๐’…โˆ™๐’†โˆ™๐’šโˆ™๐’›
๐Ÿ๐Ÿ•๐’…๐’†๐’š๐’›
c.
๏‚ง
Double the product of ๐Ÿ”๐’š and ๐Ÿ‘๐’ƒ๐’„.
We can start by finding the product of 6๐‘ฆ and 3๐‘๐‘.
Lesson 10:
Writing and Expanding Multiplication Expressions
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
6•4
๐Ÿ”โˆ™๐’šโˆ™๐Ÿ‘โˆ™๐’ƒโˆ™๐’„
๐Ÿ”โˆ™๐Ÿ‘โˆ™๐’ƒโˆ™๐’„โˆ™๐’š
๐Ÿ๐Ÿ–๐’ƒ๐’„๐’š
MP.7
๏‚ง
What does it mean to double something?
๏ƒบ
It means to multiply by 2.
๐Ÿ โˆ™ ๐Ÿ๐Ÿ–๐’ƒ๐’„๐’š
๐Ÿ‘๐Ÿ”๐’ƒ๐’„๐’š
Exercises (14 minutes)
Students match expressions on a BINGO board. Some of the expressions are simplified, and some are expanded. To
save time, provide students with a BINGO board with some of the squares already filled in. Have the remaining answers
written on a smart board, a chalkboard, or an overhead projector so that students can randomly place them on the
BINGO board. If there is not enough time for the BINGO game, these questions can be used on white boards,
chalkboards, or some form of personal boards.
Here are the clues to be given during the game, followed by the answers that are on the board.
Questions/Clues
Answers
10๐‘š
2โˆ™5โˆ™m
8โˆ™3โˆ™๐‘š
24๐‘š
Has a coefficient of 11
11๐‘š๐‘
14๐‘š๐‘
2โˆ™7โˆ™๐‘šโˆ™๐‘
(3๐‘š)(9๐‘)
27๐‘š๐‘
11๐‘š โˆ™ 2๐‘
22๐‘š๐‘
36๐‘š
2โˆ™2โˆ™3โˆ™3โˆ™๐‘š
2โˆ™2โˆ™2โˆ™5โˆ™๐‘
40๐‘
7๐‘š๐‘ โˆ™ 5๐‘ก
35๐‘š๐‘๐‘ก
18๐‘๐‘ก
2โˆ™3โˆ™3โˆ™๐‘โˆ™๐‘ก
7โˆ™2โˆ™๐‘กโˆ™2โˆ™๐‘
28๐‘๐‘ก
Has a coefficient of 5
5๐‘š๐‘๐‘ก
3โˆ™3โˆ™5โˆ™๐‘šโˆ™๐‘
45๐‘š๐‘
5๐‘š โˆ™ 9๐‘๐‘ก
45๐‘š๐‘๐‘ก
10๐‘š๐‘ โˆ™ 4๐‘ก
40๐‘š๐‘๐‘ก
1๐‘š๐‘๐‘ก
๐‘š๐‘๐‘ก
45๐‘š๐‘
3โˆ™3โˆ™5โˆ™๐‘šโˆ™๐‘
(4๐‘š๐‘)(11)
44๐‘š๐‘
54๐‘š๐‘๐‘ก
3โˆ™3โˆ™3โˆ™2โˆ™๐‘šโˆ™๐‘โˆ™๐‘ก
Has a coefficient of 3
3๐‘š
Lesson 10:
Writing and Expanding Multiplication Expressions
This work is derived from Eureka Math ™ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G6-M4-TE-1.3.0-09.2015
These answers have already been
included on premade BINGO
boards to save time. The other
answers can be randomly placed
in the remaining spaces.
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
2โˆ™2โˆ™2โˆ™3โˆ™๐‘šโˆ™๐‘
24๐‘š๐‘
(5๐‘š)(3๐‘)(2๐‘ก)
30๐‘š๐‘๐‘ก
13๐‘š๐‘
(1๐‘š๐‘)(13)
Has a coefficient of 2
2๐‘
6•4
Closing (3 minutes)
๏‚ง
What is the difference between standard form and expanded form?
๏ƒบ
๏‚ง
When we write an expression in standard form, we get rid of the operation symbol or symbols for
multiplication, and we write the factors next to each other. Sometimes we might have to multiply
numbers together before writing it next to the variable or variables. When we write an expression in
expanded form, we write the expression as a product of the factors using the “ โˆ™ ” symbol for
multiplication.
How would you describe the following terms?
1.
Factor
๏ƒบ
A number or variable that is multiplied to get a product
Variable
๏ƒบ
A letter used to represent a number
Product
๏ƒบ
The solution when two factors are multiplied
Coefficient
๏ƒบ
The numerical factor that multiplies the variable
Lesson Summary
AN EXPRESSION IN EXPANDED FORM: An expression that is written as sums (and/or differences) of products whose
factors are numbers, variables, or variables raised to whole number powers is said to be in expanded form. A single
number, variable, or a single product of numbers and/or variables is also considered to be in expanded form.
Note: Each summand of an expression in expanded form is called a term, and the number found by multiplying just the
AN EXPRESSION IN STANDARD FORM: An expression that is in expanded form where all
numbers in a term together is called the coefficient of the term. After the word term is defined, students can be shown
like-terms have been collected is said to be in standard form.
what it means to “collect like terms” using the distributive property.
Expressions in expanded form are analogous to polynomial expressions that are written as a sum of monomials. There
are two reasons for introducing this term instead of the word polynomial: (1) In the Common Core State Standards, the
word polynomial cannot be formally defined before high school, but the idea behind the word is needed much sooner.
(2) The progressions are very clear about not asking problems that state, “Simplify.” However, they do describe
standard form in the progressions, so students may be asked to put their answers in standard form. To get to standard
form, students are asked to expand the expression and then collect like terms.
Lesson 10:
Writing and Expanding Multiplication Expressions
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Lesson 10
6•4
AN EXPRESSION IN STANDARD FORM: An expression that is in expanded form where all like terms have been collected is said
to be in standard form.
Note: Students cannot be asked to “simplify,” but they can be asked to “put an expression in standard form” or “expand
the expression and collect all like terms.”
Exit Ticket (4 minutes)
Lesson 10:
Writing and Expanding Multiplication Expressions
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
Name
6•4
Date
Lesson 10: Writing and Expanding Multiplication Expressions
Exit Ticket
1.
2.
Rewrite the expression in standard form (use the fewest number of symbols and characters possible).
a.
5๐‘” โˆ™ 7โ„Ž
b.
3โˆ™4โˆ™5โˆ™๐‘šโˆ™๐‘›
Name the parts of the expression. Then, write it in expanded form.
a.
14๐‘
b.
30๐‘—๐‘˜
Lesson 10:
Writing and Expanding Multiplication Expressions
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
6•4
Exit Ticket Sample Solutions
1.
Rewrite the expression in standard form (use the fewest number of symbols and characters possible).
a.
๐Ÿ“๐’ˆ โˆ™ ๐Ÿ•๐’‰
๐Ÿ‘๐Ÿ“๐’ˆ๐’‰
b.
๐Ÿ‘โˆ™๐Ÿ’โˆ™๐Ÿ“โˆ™๐’Žโˆ™๐’
๐Ÿ”๐ŸŽ๐’Ž๐’
2.
Name the parts of the expression. Then, write it in expanded form.
a.
๐Ÿ๐Ÿ’๐’ƒ
๐Ÿ๐Ÿ’ โˆ™ ๐’ƒ or ๐Ÿ โˆ™ ๐Ÿ• โˆ™ ๐’ƒ
๐Ÿ๐Ÿ’ is the coefficient, ๐’ƒ is the variable, and ๐Ÿ๐Ÿ’๐’ƒ is a term and the product of ๐Ÿ๐Ÿ’ × ๐’ƒ.
b.
๐Ÿ‘๐ŸŽ๐’‹๐’Œ
๐Ÿ‘๐ŸŽ โˆ™ ๐’‹ โˆ™ ๐’Œ or ๐Ÿ โˆ™ ๐Ÿ‘ โˆ™ ๐Ÿ“ โˆ™ ๐’‹ โˆ™ ๐’Œ
๐Ÿ‘๐ŸŽ is the coefficient, ๐’‹ and ๐’Œ are the variables, and ๐Ÿ‘๐ŸŽ๐’‹๐’Œ is a term and the product of ๐Ÿ‘๐ŸŽ โˆ™ ๐’‹ โˆ™ ๐’Œ.
Problem Set Sample Solutions
1.
Rewrite the expression in standard form (use the fewest number of symbols and characters possible).
a.
๐Ÿ“โˆ™๐’š
๐Ÿ“๐’š
b.
๐Ÿ•โˆ™๐’…โˆ™๐’†
๐Ÿ•๐’…๐’†
c.
๐Ÿ“โˆ™๐Ÿโˆ™๐Ÿโˆ™๐’šโˆ™๐’›
๐Ÿ๐ŸŽ๐’š๐’›
d.
๐Ÿ‘โˆ™๐Ÿ‘โˆ™๐Ÿโˆ™๐Ÿ“โˆ™๐’…
๐Ÿ—๐ŸŽ๐’…
2.
Write the following expressions in expanded form.
a.
๐Ÿ‘๐’ˆ
๐Ÿ‘โˆ™๐’ˆ
b.
๐Ÿ๐Ÿ๐’Ž๐’‘
๐Ÿ๐Ÿ โˆ™ ๐’Ž โˆ™ ๐’‘
Lesson 10:
Writing and Expanding Multiplication Expressions
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c.
Lesson 10
6•4
๐Ÿ๐ŸŽ๐’š๐’›
๐Ÿ๐ŸŽ โˆ™ ๐’š โˆ™ ๐’› or ๐Ÿ โˆ™ ๐Ÿ โˆ™ ๐Ÿ“ โˆ™ ๐’š โˆ™ ๐’›
d.
๐Ÿ๐Ÿ“๐’‚๐’ƒ๐’„
๐Ÿ๐Ÿ“ โˆ™ ๐’‚ โˆ™ ๐’ƒ โˆ™ ๐’„ or ๐Ÿ‘ โˆ™ ๐Ÿ“ โˆ™ ๐’‚ โˆ™ ๐’ƒ โˆ™ ๐’„
3.
Find the product.
a.
๐Ÿ“๐’… โˆ™ ๐Ÿ•๐’ˆ
๐Ÿ‘๐Ÿ“๐’…๐’ˆ
b.
๐Ÿ๐Ÿ๐’‚๐’ƒ โˆ™ ๐Ÿ‘๐’„๐’…
๐Ÿ‘๐Ÿ”๐’‚๐’ƒ๐’„๐’…
Lesson 10:
Writing and Expanding Multiplication Expressions
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Lesson 10:
Writing and Expanding Multiplication Expressions
This work is derived from Eureka Math ™ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G6-M4-TE-1.3.0-09.2015
Lesson 10
6•4
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
2โ—5โ—๐‘š
6•4
35๐‘š๐‘๐‘ก
45๐‘š๐‘
40๐‘
24๐‘š
2โ—7โ—๐‘šโ—๐‘
11๐‘š๐‘
28๐‘๐‘ก
22๐‘š๐‘
27๐‘š๐‘
5๐‘š๐‘๐‘ก
Lesson 10:
2โ—3โ—3โ—๐‘โ—๐‘ก
Writing and Expanding Multiplication Expressions
This work is derived from Eureka Math ™ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G6-M4-TE-1.3.0-09.2015
2โ—2โ—3โ—3โ—๐‘š
45๐‘š๐‘๐‘ก
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Lesson 10
NYS COMMON CORE MATHEMATICS CURRICULUM
22๐‘š๐‘
40๐‘
28๐‘๐‘ก
2โ—5โ—๐‘š
45๐‘š๐‘
24๐‘š
2โ—7โ—๐‘šโ—๐‘
6•4
5๐‘š๐‘๐‘ก
Lesson 10:
Writing and Expanding Multiplication Expressions
This work is derived from Eureka Math ™ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G6-M4-TE-1.3.0-09.2015
2โ—2โ—3โ—3โ—๐‘š
35๐‘š๐‘๐‘ก
45๐‘š๐‘๐‘ก
27๐‘š๐‘
11๐‘š๐‘
2โ—3โ—3โ—๐‘โ—๐‘ก
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45๐‘š๐‘
40๐‘
2 โ— 3 โ— 3 โ— ๐‘ โ—๐‘ก
5๐‘š๐‘๐‘ก
24๐‘š
22๐‘š๐‘
11๐‘š๐‘
45๐‘š๐‘๐‘ก
27๐‘š๐‘
Writing and Expanding Multiplication Expressions
This work is derived from Eureka Math ™ and licensed by Great Minds. ©2015 Great Minds. eureka-math.org
This file derived from G6-M4-TE-1.3.0-09.2015
2 โ— 2 โ—3 โ— 3 โ— ๐‘š
28๐‘๐‘ก
2โ—7โ—๐‘šโ—๐‘
2โ—5โ—๐‘š
Lesson 10:
6•4
35๐‘š๐‘๐‘ก
118
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