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Substituting to Evaluate Addition and Subtraction Expressions




 


Videos to help Grade 6 students learn how to develop expressions involving addition and subtraction from real-world problems and evaluate these expressions for given values.

New York State Common Core Math Module 4, Grade 6, Lesson 19

Related Topics:
Lesson Plans and Worksheets for Grade 6

Lesson Plans and Worksheets for all Grades

More Lessons for Grade 6

Common Core For Grade 6

Lesson 19 Student Outcomes

Students develop expressions involving addition and subtraction from real-world problems.

Students evaluate these expressions for given values.

Opening Exercise

My older sister is exactly two years older than I am. Sharing a birthday is both fun and annoying. Every year on our birthday we have a party, which is fun, but she always brags that she is two years older than I am, which is annoying.
Shown below is a table of our ages, starting when I was born:

1. Looking at the table, what patterns do you see?
2. On the day I turned 8 years old, how old was my sister?
3. How do you know?
4. On the day I turned 16 years old, how old was my sister?
5. How do you know?
6. Do we need to extend the table to calculate these answers?

Example 1:

a. What if you don’t know how old I am? Let’s use a variable for my age. Let Y = my age in years. Can you develop an expression to describe how old my sister is?

Example 2:

a. How old was I when my sister was 6 years old?
b. How old was I when my sister was 15 years old?
c. How do you know?
d. Look at the table in Example 2. If you know my sister’s age, can you determine my age?
e. If we use the variable G for my sister’s age in years, what expression would describe my age in years?

Exercises 1–3

1. Noah and Carter are collecting box tops for their school. They each bring in1 per day starting on the first day of school. However, Carter had a head start because his aunt sent him 15 box tops before school began. Noah’s grandma saved 10 box tops, and Noah added those on his first day.

a. Fill in the missing values that indicate the total number of box tops each boy brought to school.
b. If we let D be the number of days since the new school year began, on day D of school, how many box tops will Noah have brought to school?
c. On day D of school, how many box tops will Carter have brought to school?
d. On day 10 of school, how many box tops will Noah have brought to school?
e. On day 10 of school, how many box tops will Carter have brought to school?

2. Each week the Primary School recycles 200 pounds of paper. The Intermediate School also recycles the same amount but had another300 pounds left over from summer school. The Intermediate School custodian added this 300 extra pounds to the first recycle week.

a. Number the weeks and record the amount of paper recycled by both schools
b. If this trend continues, what will be the total amount collected for each school on Week 10?

3. Shelly and Kristen share a birthday, but Shelly is5 years older.

a. Make a table showing their ages every year, beginning when Kristen was born.
b. If Kristen is 16 years old, how old is Shelly?
c. If Kristen is K years old, how old is Shelly?
d. If Shelly is 5 years old, how old is Kristen?







Rotate to landscape screen format on a mobile phone or small tablet to use the Mathway widget, a free math problem solver that answers your questions with step-by-step explanations.


You can use the free Mathway calculator and problem solver below to practice Algebra or other math topics. Try the given examples, or type in your own problem and check your answer with the step-by-step explanations.


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