# Writing and Evaluating 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 18

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Lesson Plans and Worksheets for Grade 6
Lesson Plans and Worksheets for all Grades

Lesson 18 Student Outcomes

• Students use variables to write expressions involving addition and subtraction from real-world problems.
• Students evaluate these expressions when given the value of the variable.

Opening Exercise

How can we show a number increased by 3?
Can you prove this using a model?

Example 1: The Importance of Being Specific in Naming Variables
When naming variables in expressions, it is important to be very clear about what they stand for. The units of measure must be included if something is measured.

Exercises
1 - 2. Read the variable in the table and improve the description given, making it more specific.

Example 2: Writing and Evaluating Addition and Subtraction Expressions
Read each story problem. Identify the unknown quantity, and write the addition or subtraction expression that is described. Finally, evaluate your expression using the information given in column four.

Gregg has two more dollars than his brother Jeff. Write an expression for the amount of money Gregg has.

Gregg has two more dollars than his brother Jeff. Write an expression for the amount of money Jeff has.

Abby read 8 more books than Kristen in the first marking period. Write an expression for the number of books Abby read.

Abby read 6 more books than Kristen in the second marking period. Write an expression for the number of books Kristen read.

Daryl has been teaching for one year longer than Julie. Write an expression for the number of years that Daryl has been teaching.

Ian scored 4 fewer goals than Julia in the first half of the season. Write an expression for the number of goals Ian scored.

Ian scored 3 fewer goals than Julia in the second half of the season. Write an expression for the number of goals Julia scored.

Ian scored 3 fewer goals than Julia in the second half of the season. Write an expression for the number of goals Julia scored.

Problem Set
Read each story problem. Identify the unknown quantity, and write the addition or subtraction expression that is described. Finally, evaluate your expression using the information given in column four.
Sammy has two more baseballs than his brother Ethan. Evaluate the Expression If: Sammy has 9 baseballs.

Ella wrote 8 more stories than Anna in the fifth grade. Evaluate the Expression If: Anna wrote 10 stories in the fifth grade.

Lisa has been dancing for 3 more years than Danika. Evaluate the Expression If: Danika has been dancing for 6 years.

The New York Rangers scored 2 fewer goals than the Buffalo Sabres last night. Evaluate the Expression If: The Rangers scored 3 goals last night.

George has gone camping 3 times fewer than Dave. Evaluate the Expression If: George has gone camping 8 times.

If George went camping 15 times, how could you figure out how many times Dave went camping?

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