Lesson 17

Modeling with Inequalities

Problem 1

28 students travel on a field trip. They bring a van that can seat 12 students. Elena and Kiran’s teacher asks other adults to drive cars that seat 3 children each to transport the rest of the students.

Elena wonders if she should use the inequality \(12+3n>28\) or \(12+3n\geq28\) to figure out how many cars are needed. Kiran doesn’t think it matters in this case. Do you agree with Kiran? Explain your reasoning.

Solution

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Problem 2

  1. In the cafeteria, there is one large 10-seat table and many smaller 4-seat tables. There are enough tables to fit 200 students. Write an inequality whose solution is the possible number of 4-seat tables in the cafeteria.
  2. 5 barrels catch rainwater in the schoolyard. Four barrels are the same size, and the fifth barrel holds 10 liters of water. Combined, the 5 barrels can hold at least 200 liters of water. Write an inequality whose solution is the possible size of each of the 4 barrels.
  3. How are these two problems similar? How are they different?

Solution

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Problem 3

Solve each equation.

  1. \(5(n-4)=\text-60\)
  2. \(\text-3t+ \text-8=25\)
  3. \(7p-8=\text-22\)
  4. \(\frac25(j+40)=\text-4\)
  5. \(4(w+1)=\text-6\)

Solution

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(From Unit 6, Lesson 9.)

Problem 4

Select all the inequalities that have the same graph as \(x<4\).

A:

\(x<2\)

B:

\(x+6<10\)

C:

\(5x<20\)

D:

\(x-2>2\)

E:

\(x<8\)

Solution

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(From Unit 6, Lesson 13.)

Problem 5

A 200 pound person weighs 33 pounds on the Moon.

  1. How much did the person’s weight decrease?

  2. By what percentage did the person’s weight decrease?

Solution

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(From Unit 4, Lesson 12.)