Recycling Rates: Cracking Percent Word Problems!

Mathematics Grades 7th Grade 2:49 Video
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Lesson Description

Learn how to solve percent word problems using real-world examples like recycling rates. Master converting fractions to decimals and percentages to understand data and make informed decisions.

Video Resource

Percent word problem example 2 | Decimals | Pre-Algebra | Khan Academy

Khan Academy

Duration: 2:49
Watch on YouTube

Key Concepts

  • Converting fractions to decimals
  • Converting decimals to percentages
  • Understanding the meaning of percent as 'per hundred'
  • Solving word problems involving percentages

Learning Objectives

  • Students will be able to convert a fraction to a decimal using long division.
  • Students will be able to convert a decimal to a percentage by multiplying by 100 or moving the decimal point.
  • Students will be able to solve percent word problems using fractions and proportions.

Educator Instructions

  • Introduction (5 mins)
    Begin by discussing the importance of recycling and its impact on the environment. Ask students if they know the approximate recycling rates in their community or state. Introduce the problem: 'In the United States, 13 out of every 20 cans are recycled. What percent of cans are recycled?' Explain that this lesson will teach them how to solve this type of problem.
  • Video Explanation (10 mins)
    Play the Khan Academy video 'Percent word problem example 2 | Decimals | Pre-Algebra | Khan Academy'. Instruct students to take notes on the two methods presented: converting the fraction to a decimal using long division and setting up a proportion.
  • Guided Practice (15 mins)
    Work through the problem from the video again, step-by-step, on the board. Emphasize the two methods: 1) dividing the numerator by the denominator to get a decimal, then multiplying by 100 to convert to a percentage; and 2) setting up a proportion (13/20 = x/100) and solving for x. Discuss the advantages and disadvantages of each method.
  • Independent Practice (15 mins)
    Provide students with similar word problems. For example: * 'A store is having a sale where 3 out of every 5 items are discounted. What percentage of items are discounted?' * '22 out of 25 students in a class passed their math test. What percentage of students passed the test?' Have students solve these problems using either method discussed. Circulate to provide assistance and answer questions.
  • Wrap-up and Assessment (5 mins)
    Review the key steps in solving percent word problems. Assign a short quiz (multiple choice and fill-in-the-blank) to assess student understanding.

Interactive Exercises

  • Real-World Data Collection
    Have students research recycling rates in their local area or state. They can then create their own percent word problems based on this data and share them with the class.
  • Online Practice
    Assign the practice exercises on Khan Academy related to percent word problems. This allows for personalized learning and immediate feedback.

Discussion Questions

  • What does 'percent' mean?
  • Can you think of other real-world situations where you might need to calculate percentages?
  • Which method for solving percent word problems do you prefer, and why?

Skills Developed

  • Problem-solving
  • Proportional reasoning
  • Fraction to decimal conversion
  • Decimal to percentage conversion
  • Application of mathematical concepts to real-world scenarios

Multiple Choice Questions

Question 1:

What does 'percent' literally mean?

Correct Answer: Per hundred

Question 2:

To convert a decimal to a percentage, you should:

Correct Answer: Multiply by 100

Question 3:

If 1 out of 4 apples are green, what percentage of the apples are green?

Correct Answer: 25%

Question 4:

Which of the following is equivalent to 0.75 as a percentage?

Correct Answer: 75%

Question 5:

If you recycle 3 out of 10 bottles, what percentage of bottles did you recycle?

Correct Answer: 30%

Question 6:

What is 1/2 as a percentage?

Correct Answer: 50%

Question 7:

To convert a fraction to a decimal, you should:

Correct Answer: Divide the numerator by the denominator

Question 8:

20 out of 50 students are wearing glasses. What percentage of students are wearing glasses?

Correct Answer: 40%

Question 9:

If 0.90 represents a percentage, what is that percentage?

Correct Answer: 90%

Question 10:

In a class, 15 out of 25 students participate in sports. What percentage of students participate in sports?

Correct Answer: 60%

Fill in the Blank Questions

Question 1:

Percent means per ________.

Correct Answer: hundred

Question 2:

To change a decimal to a percentage, you multiply by ________.

Correct Answer: 100

Question 3:

The fraction 1/4 is equal to ________ %.

Correct Answer: 25

Question 4:

0.5 as a percentage is ________ %.

Correct Answer: 50

Question 5:

If 7 out of 10 people like pizza, then ________ % of people like pizza.

Correct Answer: 70

Question 6:

To change a fraction to a decimal, you ________ the numerator by the denominator.

Correct Answer: divide

Question 7:

The percentage equivalent of 0.25 is ________%.

Correct Answer: 25

Question 8:

________ percent is the same as one half.

Correct Answer: 50

Question 9:

If 30 out of 100 students are absent, ________% of students are absent.

Correct Answer: 30

Question 10:

Writing 0.6 as a percent results in ________%.

Correct Answer: 60

Educational Standards

7.N.1:[Standard] Read, write, represent, and compare rational numbers, expressed as integers, fractions, and decimals. Explain and apply the concept of absolute value. 7.N.1.2:[Objective] Recognize and generate equivalent representations of rational numbers, including equivalent fractions. 7.A.2.2:[Objective] Solve multi-step problems with proportional relationships (e.g., distance-time, percent increase or decrease, discounts, tips, unit pricing, mixtures and concentrations, similar figures, other mathematical situations).

Teaching Materials

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