Mastering Decimals: Adding and Subtracting in Real-World Scenarios

Mathematics Grades 7th Grade 2:19 Video
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Lesson Description

Learn how to confidently add and subtract decimals in word problems, just like managing a bank account!

Video Resource

Adding and subtracting decimals word problem | Decimals | Pre-Algebra | Khan Academy

Khan Academy

Duration: 2:19
Watch on YouTube

Key Concepts

  • Decimal Addition
  • Decimal Subtraction
  • Real-World Application of Decimals
  • Problem-Solving Strategies

Learning Objectives

  • Students will be able to accurately add and subtract decimals in the context of word problems.
  • Students will be able to identify the operations (addition or subtraction) needed to solve a given decimal word problem.
  • Students will be able to apply decimal operations to solve real-world problems related to finance.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the basics of decimal place value. Briefly discuss real-world scenarios where decimals are used (e.g., money, measurements). Engage students by asking them where they encounter decimals in their daily lives.
  • Video Viewing (10 mins)
    Play the Khan Academy video "Adding and subtracting decimals word problem | Decimals | Pre-Algebra | Khan Academy". Instruct students to take notes on the steps the narrator uses to solve the problem.
  • Guided Practice (15 mins)
    Work through a similar example problem on the board, emphasizing aligning decimal points and performing the correct operations. Break down each step and explain the reasoning behind it. For example: Maria has $23.45, she finds $5.60 and spends $10.20. How much does she have left?
  • Independent Practice (15 mins)
    Provide students with a worksheet containing several word problems involving adding and subtracting decimals. Encourage students to work individually or in pairs to solve the problems. Provide assistance as needed.
  • Review and Wrap-Up (5 mins)
    Review the answers to the independent practice problems. Address any remaining questions or misconceptions. Summarize the key concepts learned in the lesson.

Interactive Exercises

  • Decimal Bank Account Simulation
    Create a simulation where students manage a virtual bank account, making deposits and withdrawals using decimals. Track their balance and assess their ability to perform the correct operations.
  • Online Practice Games
    Use online resources like Khan Academy to assign practice exercises on adding and subtracting decimals in word problems. Monitor student progress and provide feedback.

Discussion Questions

  • Why is it important to align the decimal points when adding or subtracting decimals?
  • Can you think of other real-world situations where adding and subtracting decimals is necessary?
  • How does estimating your answer before solving help you determine if your final answer is reasonable?

Skills Developed

  • Problem-Solving
  • Critical Thinking
  • Decimal Operations
  • Real-World Application of Math

Multiple Choice Questions

Question 1:

Sarah has $12.50. She earns $5.75 for doing chores. Then she spends $3.25 on candy. How much money does Sarah have left?

Correct Answer: $14.00

Question 2:

What is the first step in solving a decimal addition or subtraction word problem?

Correct Answer: Read the problem carefully.

Question 3:

A store sells apples for $1.50 each and bananas for $0.75 each. If you buy 3 apples and 2 bananas, how much will you spend?

Correct Answer: $5.00

Question 4:

Which of the following is the same as $300?

Correct Answer: All of the above

Question 5:

What does it mean to 'deposit' money into an account?

Correct Answer: To add money

Question 6:

What does it mean to 'withdraw' money into an account?

Correct Answer: To take money out

Question 7:

John has $25.00 and spends $3.50 on chips and $4.25 on a drink. How much money does he have left?

Correct Answer: $17.25

Question 8:

A notebook costs $2.75 and a pen costs $1.25. How much will 3 notebooks and 2 pens cost?

Correct Answer: $11.75

Question 9:

Amy has $50.00 in her bank account. She deposits $25.50 and then withdraws $15.00. How much money does she have left?

Correct Answer: $55.50

Question 10:

When adding or subtracting decimals, which place value should you start with?

Correct Answer: The hundredths place

Fill in the Blank Questions

Question 1:

When adding or subtracting decimals, it is important to line up the ________ ________.

Correct Answer: decimal points

Question 2:

A ________ is one hundredth of a dollar.

Correct Answer: penny

Question 3:

Adding money to your bank account is called a ________.

Correct Answer: deposit

Question 4:

Taking money out of your bank account is called a ________.

Correct Answer: withdrawal

Question 5:

$5.00 is the same as ________ cents.

Correct Answer: 500

Question 6:

Before solving, ________ your answer can help you make sure your answer is correct.

Correct Answer: estimating

Question 7:

When you deposit money in an account, you are ________ to the account.

Correct Answer: adding

Question 8:

When you withdraw money from an account, you are ________ from the account.

Correct Answer: subtracting

Question 9:

The number to the right of the decimal point is called the ________ place.

Correct Answer: tenths

Question 10:

Trailing ________ after the decimal do not change the value of the number.

Correct Answer: zeroes

Educational Standards

7.N.2.5:[Objective] Model and solve problems using rational numbers involving addition, subtraction, multiplication, division, and positive integer exponents. 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.

Teaching Materials

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