Write Algebraic Expressions

​Lesson 4.1

Write and Evaluate Algebraic Expressions​

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​Definition:

Variable: A placeholder for a number we do not know yet. A variable can be anything, but we commonly see them written as letters.​

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Expression: An expression is like a math sentence. It is a combination of variables and terms (numbers).​

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Subject | Subject

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​Key Concept:

We can use variables to help us write and solve word problems. We will see this in problems about weight, money and change over time as well as many other topics.​

Subject | Subject

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​The KWL method:

​What I know?

​What I want to know?

​What I learned?

Multiple Choice

T1-Misumi started with $217 in her bank account. She deposits $25.50 each week and never withdraws any money. What expression can Misumi use to determine her account balance after w weeks?

• 217 - 25.50 * w
• 217 + 25.50 + w
• 25.50 * w - 217
• 217 + 25.50 * w

Multiple Choice

T2-The cost to rent a scooter is $15.50 per hour and the cost to rent a watercraft is $22.80 per hour. What is the algebraic expression

• 15.5s - 22.8w

• 15.5s + 22.8w

• 15.5+ 22.8w

• 15.5s + 22.8

Multiple Choice

Use the expression 15.5s + 22.8w to determine how much it would cost to rent a scooter for 𝟥and half hours and a watercraft for 𝟣and 3 fourth hours?

• 76.30

• 85.75
• 102.50
• 94.15

Multiple Select

T3-Emelia earns $8.74 per hour plus a gas allowance of $3.50 per day at her job. How much does Emelia’s job pay in a day when she works 𝟧.5 hours? Write an expression and evaluate for 𝟧.5 hours.

• 8.74 h+3.50

• 8.74 + 3.50 h

• $51.57

• $56.25

​4: A tank containing 35 gallons of water is leaking at a rate of 1/4 gallons per minute. Write an expression for this situation.

Multiple Choice

A tank already has 20 gallons of water in it. It is being filled at a rate of 1/2 gallon per minute. What expression models this situation?

• 20m - 1/2

• 20 - 1/2m

• 20 + 1/2m

• 20m + 1/2

​Example: A tree that began at 6 feet and increases by 2 feet per year. Let y represent the number of years.

​Example: The expression -120 + 13m represents a submarine that began at a depth of 120 feet below sea level and ascended at a rate of 13 feet per minute. What was the depth of the submarine after 6 minutes?

Multiple Choice

Write an expression to model a person who began at 4ft and grows 1/4 ft per year.

• 4y + 1/4

• 4y - 1/4

• 4 + (1/4)y

• 4 - (1/4)y

Multiple Choice

The expression -150 + 10m represents a submarine's depth as it is rising to the surface. What is the submarine's position after 10 minutes.

• -100

• -250

• -50

• 50

Multiple Choice

Evaluate the expression 3x + 5 for x = 6

• 14

• 23

• 13

• 18

Multiple Choice

Evaluate the expression for m = 4

0.5m - 8

• 10

• -3.5

• -6

• 6

​Conclusion: Write two complete sentences about what you learned.