Estimating with Decimals

Lesson Overview

Objective

Students will learn to estimate, add, and subtract decimals, developing their ability to approximate values and perform calculations efficiently. The focus will be on aligning with California Common Core State Standards for Mathematics Grade 6, specifically in the areas of Number Sense and Mathematical Operations.

Standards

CA Common Core State Standards - Mathematics

• Grade 6 Number System:
  • CCSS.MATH.CONTENT.6.NS.B.3: Fluently add, subtract, multiply, and divide multi-digit decimals using the standard algorithm for each operation.

Materials

• Whiteboard and markers
• Student notebooks
• Estimation bingo cards
• Calculators (optional, for checking work)
• Small whiteboards and markers for each student
• A set of decimal playing cards

Lesson Sequence

Introduction (5 minutes)

1. Warm-Up Activity: Decimal Quick-Think

   • Ask students: "What is an estimate?" Let them discuss in pairs.
   • Write a decimal on the board (e.g., 7.56) and ask them to estimate this to the nearest whole number. Discuss strategies.

2. Briefly revisit why estimation is important – it helps to quickly understand approximate values in real-life situations such as shopping.

Direct Instruction (10 minutes)

1. Review Key Concepts

   • Explain rounding rules for decimals (e.g., round 7.56 to 8).
   • Model an estimation strategy: Round, then add or subtract.

2. Example Problem

   • Demonstrate on the board: Estimate the sum of 5.97 + 6.34 by rounding to the nearest whole number first (6 + 6 = 12).

3. Check for Understanding

   • Have students estimate the difference for 9.83 - 1.76 on their mini whiteboards. Review and discuss answers.

Guided Practice (10 minutes)

1. Estimation Bingo

   • Hand out bingo cards with sums and differences of decimals that simplify to single-digit whole numbers.
   • Call out problems that require estimation to the nearest whole number.
   • Students estimate and mark their boards if they have the answer.

2. Walk around and observe students' strategies, providing support as needed.

Independent Practice (10 minutes)

1. Decimal Card Games

   • Pair students and distribute the decimal playing cards.
   • Each pair picks two cards and estimates their sum or difference.
   • Players check each other's work with calculators to confirm the actual calculations.

2. Encourage students to explain their estimation strategy to their partners.

Conclusion (5 minutes)

1. Class Reflection and Discussion

   • Discuss: How did estimation help in calculations today?
   • Have students share a strategy they found useful.

2. Exit Ticket

   • On a sticky note, students write their estimate for 8.56 – 2.19 and the strategy they used.
   • Collect these as they leave for quick assessment of understanding.

Extension Activities

• Real-world Connection: Ask students to estimate the total cost of grocery items with prices given to two decimal places.
• Challenge Problems: Provide more complex decimals for students who master the concepts quickly.

Assessment

• Observe student participation in activities and discussions.
• Review exit tickets to assess understanding of estimation and calculation strategies.
• Use feedback from games to gauge student proficiency in estimating and performing operations with decimals.