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6.EE.B.5Common CoreMathExpressions and EquationsGrade 6

6.EE.B.5: Solving Equations and Inequalities by Testing Values

In plain English: 6.EE.B.5 is the Common Core grade 6 math standard that asks students to see solving an equation or inequality as answering a question: which values from a given set, if any, make it true? Students substitute each value, decide true or false, and learn that a set can hold one solution, several or none. It prepares for solving one-step equations in 6.EE.B.7.

Understand solving an equation or inequality as a process of answering a question: which values from a specified set, if any, make the equation or inequality true? Use substitution to determine whether a given number in a specified set makes an equation or inequality true.

Common Core State Standards for Mathematics · Domain: Expressions and Equations (EE) · Cluster: Reason about and solve one-variable equations and inequalities.
Also written as 6.EE.5 · Official standard

01

Lesson Plan

50-65 min

Overview

Students learn that solving an equation or inequality means answering a question: which values make it true? An equation is a statement that two expressions are equal, such as x + 8 = 15. An inequality is a statement that compares two expressions with a symbol such as < (less than), > (greater than), ≤ (less than or equal to) or ≥ (greater than or equal to). A variable is a letter that stands for a number, and a solution is a value of the variable that makes the statement true.

In this lesson, the possible values always come from a specified set: a short list of numbers written inside braces, such as {5, 6, 7, 8}. Students use substitution (replacing the variable with a number) to test each value, compute both sides, and decide whether the statement is true or false. They see the three cases the standard's words "if any" point to: a set can contain exactly one solution, several solutions (common with inequalities), or no solution at all. All numbers are whole numbers, simple fractions or decimals, and students test values instead of using formal solving steps, which come next in 6.EE.B.7.

Learning Objectives

By the end of this lesson, students will be able to:

  • Explain that solving an equation or inequality means finding which values, if any, make it true
  • Use substitution to decide whether a given number makes an equation true
  • Use substitution to decide whether a given number makes an inequality true, including values that make both sides equal
  • Find every solution in a specified set, and recognize when a set contains no solution
  • Decide whether solutions found by substitution make sense in a real-world situation

Prior Knowledge Required

Students should already be comfortable with:

  • Evaluating expressions with parentheses and the order of operations 5.OA.A.1
  • Adding, subtracting, multiplying and dividing decimals 6.NS.B.3
  • Reading inequality statements as positions on a number line 6.NS.C.7a
  • Writing expressions with letters standing for numbers 6.EE.A.2a
  • Evaluating expressions at specific values of their variables 6.EE.A.2c

Lesson Procedure

50-65 minutes of class time across 5 phases.

  1. Warm-Up5-10 minutes

    Write four numbers on the board: 4, 7, 9 and 12. Read the riddle aloud and give students one minute to think.

    Warm-Up Prompt

    "I am thinking of a number from the list 4, 7, 9, 12. When I add 6 to my number, I get 15. Which number is it? Now suppose the sum were 11 instead. Which number from the list works then?"

    Collect answers and ask how students found them. Most will try the numbers one at a time: 4 + 6 = 10, 7 + 6 = 13, 9 + 6 = 15. So the first riddle's number is 9. For the second riddle, no number on the list works: the sums are 10, 13, 15 and 18, and none of them is 11. Tell students that trying each number is a real mathematical method called substitution, and that "none of them works" is a correct and complete answer when the list is fixed ahead of time.

  2. Direct Instruction15-20 minutes

    Solving as answering a question. Write n + 6 = 15 and say: an equation says two amounts are equal. The letter n is a variable, a symbol that stands for a number. To solve the equation is to answer the question "which values of n make this true?" When the values must come from a specified set, such as {4, 7, 9, 12}, we test each one. A value that makes the statement true is a solution. Show the four steps of substitution:

    1. Copy the equation or inequality.
    2. Substitute: replace the variable with the value you are testing. Write the value in parentheses when it is multiplied, for example 3y with y = 5 becomes 3(5).
    3. Compute each side, following the order of operations.
    4. Decide: is the statement true or false? Record the value as a solution only if it is true.
    • Equation with one solution in the set

      Which value from the set {5, 6, 7, 8} makes x + 8 = 15 true?

      Equation: 5 + 8 = 13 (false), 6 + 8 = 14 (false), 7 + 8 = 15 (true), 8 + 8 = 16 (false). The solution is 7.

    • Equation with no solution in the set

      Which values from the set {5, 6, 7}, if any, make 3y = 20 true?

      Equation: 3(5) = 15, 3(6) = 18 and 3(7) = 21 are all false, so no value in the set is a solution.

    • Inequality with several solutions

      Which values from the set {2, 4, 6, 8, 10} make 5w > 28 true?

      Equation: 5(2) = 10 and 5(4) = 20 are not greater than 28; 5(6) = 30, 5(8) = 40 and 5(10) = 50 are. The solutions are 6, 8 and 10.

    • Inequality in a real-world situation

      School play tickets cost $6 each, and Maya has $20. Which numbers of tickets from the set {0, 1, 2, 3, 4} make 6t ≤ 20 true?

      Equation: 6(0) = 0, 6(1) = 6, 6(2) = 12 and 6(3) = 18 are all at most 20, but 6(4) = 24 is not. Maya can buy 0, 1, 2 or 3 tickets.

    • Fractions in the set

      Which value from the set {1/2, 3/4, 1, 1 1/2} makes 4k = 3 true?

      Equation: 4 × 1/2 = 2, 4 × 3/4 = 3 (true), 4 × 1 = 4 and 4 × 1 1/2 = 6. The solution is 3/4.

    Three possible answers. The standard asks which values make the statement true "if any". Point to the first three examples: a set can hold exactly one solution, no solution, or several solutions. Diagram 1 shows the third example as a table, one row per value. Inequalities often have several solutions, because many numbers can be greater than 28.

    Inequality symbols. Read each symbol aloud: < is "is less than", > is "is greater than", ≤ is "is less than or equal to" and ≥ is "is greater than or equal to". Test a value that makes both sides equal: 12 ≥ 12 is true, but 12 > 12 is false. Diagram 2 shows the ticket example on a number line, with filled green dots for solutions and open red dots for values that do not work.

  3. Guided Practice15 minutes

    Pairs test every value in each set on mini whiteboards, writing one substitution per line. After each problem, one pair shows its work and the class agrees on the solutions.

    Guided practice: find every solution in the set
    ProblemStatementSpecified set
    am ÷ 3 = 12{4, 9, 36, 39}
    by - 4 < 6{8, 9, 10, 11, 12}
    c2.5 + d = 6{3, 3.5, 4}
    d2n + 1 ≥ 11{3, 4, 5, 6}

    Answers: (a) 36, because 36 ÷ 3 = 12; a student who picks 4 has divided 12 by 3 instead of testing values. (b) 8 and 9, because 8 - 4 = 4 and 9 - 4 = 5 are less than 6, but 10 - 4 = 6 is not. (c) 3.5, because 2.5 + 3.5 = 6. (d) 5 and 6, because 2(5) + 1 = 11 and 11 ≥ 11 is true, and 2(6) + 1 = 13. Listen for students who drop the value that makes both sides equal in (d), or who keep it in (b).

  4. Independent Practice10-15 minutes

    Students work alone and show every substitution. (1) Which value from {10, 11, 12, 13} makes 9 + p = 21 true? (12.) (2) Which values from {5, 6, 7}, if any, make 7r = 40 true? (None: 35, 42 and 49.) (3) Which values from {6, 8, 10, 12} make h ÷ 2 > 4 true? (10 and 12; 8 ÷ 2 = 4 is not greater than 4.) (4) Each bag of apples weighs 3 pounds, and a shelf holds at most 25 pounds. Which numbers of bags from {6, 7, 8, 9} make 3b ≤ 25 true? (6, 7 and 8; 3(9) = 27 is too heavy.) (5) Which value from {4, 6, 8} makes 15 - q = 9 true? (6.)

  5. Closure5 minutes

    Exit ticket: (1) Does x = 4 make 5 + 3x = 17 true? Show the substitution. (Yes: 5 + 3(4) = 5 + 12 = 17.) (2) Which values from {1, 2, 3, 4} make 10 - z ≥ 7 true? (1, 2 and 3; 10 - 3 = 7 counts because of the "or equal to" part.) (3) In one sentence, what does it mean to solve an equation or inequality? (Find which values, if any, make it true.)

Differentiation Strategies

For Struggling Students

  • Give a blank testing table with the columns "value", "substitute", "compute" and "true or false?", like Diagram 1, and fill in the first row together
  • Start with sets of three whole numbers and equations with one operation, then add inequalities once students test values reliably
  • Post a symbol card that reads each inequality symbol in words, with a number line example under each one

For Advanced Students

  • Ask students to write a set of five numbers that contains exactly two solutions of 3a > 14, and another set that contains none
  • Ask which whole numbers from 0 to 20 make both 2c > 9 and c + 3 < 12 true, and how they can test fewer than 21 values
  • Ask students to explain why the equation k + 4 = 10 can have only one solution, while k + 4 > 10 has many

Assessment Guidance

What to Look For

Check that students write each substitution on its own line and compute both sides before deciding true or false. Watch for three errors: reading 3y with y = 5 as the number 35 instead of 3 × 5, dropping or keeping the value that makes both sides equal for the wrong symbol (≤ and ≥ include it, < and > do not), and stopping after the first solution when an inequality has several. Students should be comfortable answering "no value in the set" and should explain it by showing every substitution.

02

Classroom Activities

3 Activities

1

True or False Card Sort

15 minPairs

Each pair gets 8 statement cards, each printed with its own set of four value cards. Pairs substitute each value and sort the value cards into two columns on the desk: "makes it true" and "makes it false". Every pair records the solutions for each card on a sticky note.

Statement Cards (8 cards)

  • Card A: n + 13 = 20, values {6, 7, 8, 9}
  • Card B: 6n = 54, values {7, 8, 9, 10}
  • Card C: n - 5 = 12, values {15, 16, 18, 19}
  • Card D: n ÷ 4 = 2.5, values {8, 9, 10, 12}
  • Card E: 2n < 13, values {5, 6, 7, 8}
  • Card F: n + 1.5 ≥ 4, values {2, 2.5, 3, 4}
  • Card G: 4n > 30, values {7, 7.5, 8, 9}
  • Card H: 18 = 3n, values {5, 6, 7, 8}

Answer Key

  • A: 7. B: 9. C: no value in the set (the solution, 17, is missing). D: 10. E: 5 and 6. F: 2.5, 3 and 4. G: 8 and 9. H: 6.

Discussion Questions

  • Which card has no solution in its set? (Card C) How did you know you were finished?
  • Which cards have more than one solution? (Cards E, F and G, the three inequalities) Why do inequalities often have more than one?
  • On Card G, 4 × 7.5 = 30. Why is 7.5 not a solution? (30 > 30 is false)
  • On Card F, why is 2.5 a solution? (2.5 + 1.5 = 4, and 4 ≥ 4 is true)

Modification for Distance Learning

Put the cards on a shared slide with two drop zones labeled "true" and "false". Pairs drag the value cards and type one substitution next to each card.

2

Stand Up If You Make It True

15 minWhole class

Hand out 13 number cards, 0 through 12, to 13 students (the rest of the class checks the work). The cards form the specified set {0, 1, 2, ..., 12}. The teacher reads a statement about k. Each card holder substitutes their number, and stands if it makes the statement true. The checkers confirm or challenge each person standing.

Statements to Read (6 rounds)

  • Round 1: k + 4 = 10 (6 stands)
  • Round 2: 3k > 20 (7, 8, 9, 10, 11 and 12 stand)
  • Round 3: k ÷ 2 = 5.5 (11 stands)
  • Round 4: 2k + 1 = 8 (nobody stands)
  • Round 5: 12 - k ≥ 9 (0, 1, 2 and 3 stand)
  • Round 6: k + k = 16 (8 stands)

Procedure

  • Before each round, card holders write their substitution on a mini whiteboard
  • After everyone stands or sits, the checkers test one standing and one sitting student out loud
  • Swap card holders and checkers after Round 3

Discussion Questions

  • In which round did nobody stand? (Round 4) Does that mean the equation is wrong?
  • Which round had the most students standing? (Round 2, with six students)
  • In Round 5, why did the student holding 3 stand even though 12 - 3 is not greater than 9?

Modification for Distance Learning

Assign each student a number and have them unmute, raise a virtual hand or type "true" in the chat when their number is a solution.

3

Does It Make Sense? Real-World Stations

20 minPairs

Pairs rotate through 4 stations. Each station card describes a situation, gives an equation or inequality and a specified set, and asks which values are solutions and what they mean in the situation.

Station Cards (4 cards)

  • Station 1, pencils: a box holds 12 pencils. Jin needs 60 pencils for the class. Which number of boxes from {4, 5, 6} makes 12p = 60 true? (5)
  • Station 2, fair ride: riders must be at least 48 inches tall. Four friends are 46, 48, 51 and 53 inches tall. Which heights make h ≥ 48 true? (48, 51 and 53)
  • Station 3, water cooler: each player drinks 2 cups from a 30-cup cooler during a game. Which team sizes from {12, 14, 16, 18} make 2n ≤ 30 true? (12 and 14)
  • Station 4, bake sale: cookies sell for $0.50 each, and the class wants to earn $40. Which numbers of cookies from {60, 75, 80, 90} make 0.50c = 40 true? (80)

Procedure

  • At each station, test every value in the set and write the substitutions on the recording sheet
  • Write one sentence that explains each solution in words, for example "48 inches is tall enough to ride"
  • Spend about 4 minutes at each station, then rotate

Discussion Questions

  • At Station 2, the friend who is exactly 48 inches tall can ride. Which part of the symbol ≥ shows that?
  • At Station 3, why do all the sets list only whole numbers?
  • Which station had exactly one solution in its set? (Stations 1 and 4)

Challenge Variation

Pairs write their own station card with a situation, a statement and a set of four values that contains exactly two solutions, then trade with another pair.

03

Diagrams & Visual Aids

2 diagrams

Diagram 1: Testing Each Value in a Set

Which values from the set {2, 4, 6, 8, 10} make 5w > 28 true? Value of w Substitute: 5w Compare with 28 True or false? w = 2 5 × 2 = 10 Is 10 > 28? false w = 4 5 × 4 = 20 Is 20 > 28? false w = 6 5 × 6 = 30 Is 30 > 28? true w = 8 5 × 8 = 40 Is 40 > 28? true w = 10 5 × 10 = 50 Is 50 > 28? true Solutions from the set: 6, 8 and 10. The values 2 and 4 are not solutions.
A testing table for the inequality 5w > 28 and the set {2, 4, 6, 8, 10}. Each row substitutes one value, computes 5w and compares the result with 28. Three values make the inequality true, so the set contains three solutions: 6, 8 and 10.

Diagram 2: Showing Solutions on a Number Line

School play tickets cost $6 each. Maya has $20. Which values of t make 6t ≤ 20 true? Number of tickets, t 0 6 × 0 = 0 true 1 6 × 1 = 6 true 2 6 × 2 = 12 true 3 6 × 3 = 18 true 4 6 × 4 = 24 false makes 6t ≤ 20 true makes 6t ≤ 20 false Maya can buy 0, 1, 2 or 3 tickets
A number line for the ticket example, 6t ≤ 20, with the set {0, 1, 2, 3, 4}. Filled green dots mark the values that make the inequality true (0, 1, 2 and 3 tickets). The open red dot at 4 marks a value that makes it false, because 4 tickets cost $24.

04

Homework Assignment

~30 min

6.EE.B.5 Homework: Which Values Make It True?

Directions: For every problem, test each value in the set by substitution. Write one line per value, compute both sides, and label it true or false. Then list the solutions, or write "no value in the set" if none work.

Part 1: Equations (Problems 1-3)

  1. Which value from the set {6, 7, 8, 9} makes 8a = 56 true? Show each substitution.
  2. Liam buys a sandwich for $4.75 and a drink, and he spends $6.00 in all. Which drink price d from the set {$1.00, $1.25, $1.50, $1.75} makes 4.75 + d = 6.00 true?
  3. Which values from the set {10, 12, 14, 16}, if any, make g - 9 = 4 true? Explain what your answer means.

Part 2: Inequalities (Problems 4-6)

  1. Which values from the set {3, 4, 5, 6, 7} make 9 + k > 14 true?
  2. A school club has $50 to spend on pizzas that cost $11 each. Which numbers of pizzas from the set {2, 3, 4, 5} make 11p ≤ 50 true? What is the greatest number of pizzas the club can buy?
  3. Ana says that 4 is the only solution of 5x ≥ 20 in the set {2, 4, 6, 8}. Is she right? Test every value and explain.

Rubric

CriterionFull Credit (2 pts)Partial Credit (1 pt)No Credit (0 pts)
SubstitutionEvery value in every set is substituted and computed correctlyOne or two values skipped or computed incorrectlyValues guessed without substitution
True or FalseEach substitution labeled correctly, including values that make both sides equalOne symbol misread (for example ≤ treated as <)Labels missing or mostly incorrect
SolutionsAll solutions listed, and "no value in the set" given where no value worksSome solutions missingSolutions missing or incorrect
ExplanationProblems 3, 5 and 6 explained in words that fit the situationExplanation given for only some problemsNo explanation

05

Quiz: 20 Questions

Interactive, with answers

Instructions

Work through the questions in order and test values by substitution. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.

Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.

0 of 20 answered · 0 correct

  1. Question 1 of 20 · Multiple Choice

    What does it mean to solve an equation such as n + 5 = 12?

  2. Question 2 of 20 · Multiple Choice

    Does n = 6 make 4n - 5 = 19 true?

  3. Question 3 of 20 · Multiple Choice

    Which value from the set {6, 7, 36, 48} makes 6c = 42 true?

  4. Question 4 of 20 · Multiple Choice

    Which values from the set {4, 5, 6}, if any, make 8m = 44 true?

  5. Question 5 of 20 · Multiple Choice

    Which values from the set {3, 5, 7, 9} make 4q > 20 true?

  6. Question 6 of 20 · Multiple Choice

    A backpack can safely hold at most 12 pounds of books. Each textbook weighs 3 pounds. Which numbers of textbooks b from the set {2, 3, 4, 5} make 3b ≤ 12 true?

  7. Question 7 of 20 · Multiple Choice

    How many values from the set {1, 2, 3, 4, 5, 6} make y + 2 ≥ 5 true?

  8. Question 8 of 20 · Multiple Choice

    Which value from the set {1/2, 2, 3, 18} makes 6 × f = 3 true?

  9. Question 9 of 20 · Multiple Choice

    Which value from the set {2.4, 3.6, 4.4, 8.4} makes w + 2.4 = 6 true?

  10. Question 10 of 20 · Multiple Choice

    Mia tested every value in the set {10, 20, 30} for the inequality 5 + p < 10 and found that none of them made it true. What can she conclude?

  11. Question 11 of 20 · Multiple Choice

    Tickets to a science museum cost $9 each. A group paid $63 in all. Which number of tickets t from the set {4, 5, 6, 7} makes 9t = 63 true?

  12. Question 12 of 20 · Multiple Choice

    Which value from the set {0.5, 1, 1.5, 2} does NOT make 3.5 + r ≤ 5 true?

  13. Question 13 of 20 · Multiple Choice

    Kai has 28 points in a reading game and earns p more points. He wins a badge when 28 + p > 40. Which values from the set {10, 12, 14} win the badge?

  14. Question 14 of 20 · Multiple Choice

    Which value from the set {3, 4, 5, 6} makes 20 ÷ n = 5 true?

  15. Question 15 of 20 · Short Answer

    Test each value in the set {12, 14, 16, 18} for the equation k ÷ 2 = 8. Which value is the solution?

  16. Question 16 of 20 · Short Answer

    Which values from the set {0, 1, 2, 3, 4, 5}, if any, make 4 + 2h < 10 true? Show your substitutions.

  17. Question 17 of 20 · Short Answer

    A phone plan includes 5 GB of data each week. Sam uses 0.75 GB each day. Which numbers of days d from the set {5, 6, 7, 8} make 0.75d ≤ 5 true? What does your answer mean?

  18. Question 18 of 20 · Short Answer

    Write a set of four whole numbers that contains no solution of x + 6 = 10. Explain how you know.

  19. Question 19 of 20 · Short Answer

    Does y = 2.5 make 4y = 10 true? Does it make 4y > 10 true? Explain.

  20. Question 20 of 20 · Short Answer

    Leo has 3 hours of free time on Saturday afternoon. Soccer practice takes 1.25 hours. Which amounts of time t from the set {1.5, 1.75, 2} for a trip to the library make 1.25 + t ≤ 3 true?

0 of 20 answered · 0 correct

06

Frequently Asked Questions

10 Questions

What does 6.EE.B.5 mean?

6.EE.B.5 means students understand solving as answering the question "which values make this equation or inequality true?" Students are given a specified set of numbers, such as {3, 5, 7, 9}, and use substitution to test each one. A value that makes the statement true is a solution. The set may contain one solution, several, or none.

Is 6.EE.B.5 about solving equations with inverse operations?

No, not yet. In 6.EE.B.5, students solve by testing values from a set, which builds the meaning of a solution. Writing and solving equations such as x + p = q and px = q with inverse operations comes next in 6.EE.B.7. Many teachers use substitution again later as a way to check answers.

What is a specified set in 6.EE.B.5?

A specified set is the list of values students are allowed to test. It is usually written in braces, such as {0, 1, 2, 3, 4}, and it can include whole numbers, fractions or decimals. In real-world problems the set often comes from the situation, such as the number of tickets someone might buy.

What does substitution mean in math?

Substitution means replacing a variable with a number and then computing. To test whether 5 makes 2b + 3 = 13 true, write 2(5) + 3 = 10 + 3 = 13. Both sides are 13, so 5 is a solution. Writing the number in parentheses keeps students from reading 2b as a two-digit number.

Can an equation or inequality have no solution in a set?

Yes. If no value in the set makes the statement true, the answer is "no value in the set". For example, no value in {1, 2, 3} makes a + 10 = 15 true, because the only solution, 5, is not in the set. The words "if any" in the standard point to this case.

Why can an inequality have more than one solution?

An inequality compares amounts instead of saying they are equal, so many numbers can make it true. For c + 2 > 6 with the set {1, 4, 6, 10}, the values 6 and 10 both work, but 4 does not, because 4 + 2 = 6 is not greater than 6. Students should test every value in the set and not stop at the first solution.

What are common mistakes with 6.EE.B.5?

A common mistake is misreading ≤ or ≥: students forget that a value making both sides equal is a solution, or they include it for < and >. Other errors include reading 3y with y = 5 as 35, stopping after the first solution, and guessing instead of showing each substitution. A testing table with one row per value prevents most of these.

How is 6.EE.B.5 tested?

Test items usually give an equation or inequality and a set, then ask which values make it true, sometimes with more than one correct answer to select. Other items ask whether a single number is a solution, or ask students to explain what a solution means in a situation. Students should show or be ready to explain their substitutions.

How does 6.EE.B.5 connect to later math?

It builds the idea that a solution is a value that makes a statement true. That idea runs through 6.EE.B.7 and 6.EE.B.8 in grade 6, multi-step equations and inequalities in 7.EE.B.4, and solving equations in Algebra I (HSA.REI.B.3). Substituting to check an answer stays useful in every later course.

How can parents help with 6.EE.B.5 at home?

Turn everyday limits into quick tests. If a car holds at most 5 passengers, ask whether 4, 5 or 6 friends fit, and why 5 counts. At the store, give a budget and ask which numbers of items stay within it. Ask your child to say each test out loud, such as "3 times $4 is $12, and $12 is less than $15, so 3 works".