Writing Equations to Model Relationships (Part 1)

ID: nobum-lunas
Created by Illustrative MathIllustrative Math
Subject: Algebra, Algebra 2
Grade: 8-9

Writing Equations to Model Relationships (Part 1)

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Problem 1

1) Large cheese pizzas cost $5 each and large one-topping pizzas cost $6 each.

Write an equation that represents the total cost, TT, of cc large cheese pizzas and dd large one-topping pizzas.

Problem 2

2) Jada plans to serve milk and healthy cookies for a book club meeting. She is preparing 12 ounces of milk and 4 cookies per person. Including herself, there are 15 people in the club. A package of cookies contains 24 cookies and costs $4.50.

A 1-gallon jug of milk contains 128 ounces and costs $3. Let nn represent number of people in the club, mm represent the ounces of milk, cc represent the number of cookies, and bb represent Jada's budget in dollars.

Select all of the equations that could represent the quantities and constraints in this situation. Write each corresponding letter in the answer box and separate letters with commas.

a) m=12(15)m = 12(15) \quad \quad b) 3m+4.5c=b3m + 4.5c = b \quad \quad c) 4n=c4n = c \quad \quad d) 4(4.50)=c4(4.50) = c \quad \quad e) b=2(3)+3(4.50)b = 2(3) + 3(4.50)

Problem 3

3) A student on the track team runs 45 minutes each day as a part of her training. She begins her workout by running at a constant rate of 8 miles per hour for aa minutes, then slows to a constant rate of 7.5 miles per hour for bb minutes.

Which equation describes the relationship between the distance she runs in miles, DD, and her running speed, in miles per hour?

a) a+b=45 a + b = 45 b) 8a+7.5b=D 8a + 7.5b = D c) 8(a60)+7.5(b60)=D 8 \left(\frac{a}{60}\right) + 7.5\left(\frac{b}{60}\right) = D d) 8(45b)+7.5b=D 8(45-b) + 7.5b = D
Problem 4

Elena bikes 20 minutes each day for exercise.

Write an equation to describe the relationship between her distance in miles, DD, and her biking speed, in miles per hour, when she bikes:

4) at a constant speed of 13 miles per hour for the entire 20 minutes

5) at a constant speed of 15 miles per hour for the first 5 minutes, then at 12 miles per hour for the last 15 minutes

6) at a constant speed of MM miles per hour for the first 5 minutes, then at NN miles per hour for the last 15 minutes

Problem 5

7) The dot plot displays the number of marshmallows added to hot cocoa by several kids. What is the MAD of the data represented in the dot plot?

A template for answering this question. Ask your instructor for an alternative.
a) 0.6 marshmallows\text{0.6 marshmallows}b) 3 marshmallows\text{3 marshmallows}c) 4 marshmallows\text{4 marshmallows}d) 5 marshmallows\text{5 marshmallows}
Problem 6

Here is a data set: 5, 10, 10, 10, 15, 100

After studying the data, the researcher realized that the value 100 was meant to be recorded as 15.

8) What happens to the mean of the data set when the 100 is changed to a 15?

9) What happens to the standard deviation of the data set when the 100 is changed to a 15?

10) For the original data set, with the 100, would the median or the mean be a better choice of measure for the center?

a) The mean.\text{The mean.}b) The median.\text{The median.}c) I need more information.\text{I need more information.}

11) Explain your reasoning.

Problem 7

12) A coach for a little league baseball team is ordering trophies for the team. Players on the team are allowed to choose between 2 types of trophies. The gold baseball trophies cost $5.99 each and the uniform baseball trophies cost $6.49 each. The team orders gg gold baseball trophies and uu uniform baseball trophies.

Write an expression that could represent the total cost of all of the trophies.

Problem 8

13) The robotics team needs to purchase $350 of new equipment. Each of the xx students on the team plans to fundraise and contribute equally to the purchase.

Which expression represents the amount that each student needs to fundraise?

a) 350x 350 - x b) 350+x 350 + x c) 350x \frac{350}{x} d) 350x 350\cdot x
Problem 9

In a trivia contest, players form teams and work together to earn as many points as possible for their team. Each team can have between 3 and 5 players. Each player can score up to 10 points in each round of the game. Elena and four of her friends decided to form a team and play a round.

Write an expression, an equation, or an inequality for each quantity described here. If you use a variable, specify what it represents.

14) the number of points, SS, that Elena’s team earns in one round.

15) If you used a variable, define it. Otherwise, write n/a.

16) the number of points, SS, Elena’s team earns in one round if every player scores between 6 and 8 points.

17) If you used a variable, define it. Otherwise, write n/a.

18) the number of points, SS Elena's team earns if each player misses one point.

19) If you used a variable, define it. Otherwise, write n/a.

20) the number of players, pp, in a game if there are 5 teams of 4 players each.

21) If you used a variable, define it. Otherwise, write n/a.

22) the number of players, pp, in a game if there are at least 3 teams.

23) If you used a variable, define it. Otherwise, write n/a.