HomeExamination QuestionsThird TermSecondary SchoolsApproximation: Rounding Off Numbers in Mathematics JSS 1 Lesson Note

Approximation: Rounding Off Numbers in Mathematics JSS 1 Lesson Note

MATHEMATICS LESSON NOTE – APPROXIMATION

Subject: Mathematics

Class: JSS 1

Term: Second Term

Week: 2

Age: 11 – 13 years

Topic: Approximation

Sub-topic: Rounding off numbers to decimal places, significant figures, and nearest whole number

Duration: 40 minutes

Behavioural Objectives

By the end of the lesson, students should be able to:

  1. Define approximation and explain its importance in mathematics.
  2. Round off numbers to a specified number of decimal places.
  3. Round off numbers to a specified number of significant figures.
  4. Approximate numbers to the nearest whole number, tenth, hundredth, and thousandth.
  5. Solve problems involving approximation in real-life situations.

Keywords

  • Approximation
  • Decimal place
  • Significant figure
  • Round-off
  • Whole number
  • Nearest tenth, hundredth, and thousandth

Set Induction

The teacher asks:

  • “If you have 19.97 liters of fuel, can you say it is approximately 20 liters?”
  • “If a trader says a product costs ₦99.95, can we call it ₦100?”
    These questions introduce approximation.

Entry Behaviour

Students have learned about place value and basic arithmetic operations.

Learning Resources and Materials

  • Place value charts
  • Number cards
  • Calculator
  • Flashcards with decimal and whole numbers

Reference Books

  • Lagos State Scheme of Work
  • Essential Mathematics for JSS 1
  • New General Mathematics for JSS 1

Instructional Materials

  • Charts showing rounding rules
  • Numbered flashcards
  • Whiteboard and markers

Content

Definition and Meaning of Approximation

Approximation is rounding a number to make calculations easier. It is useful in daily life for budgeting, measuring, and estimating.

Types of Approximation

  1. Rounding Off to Decimal Places (d.p.)

    • Example: 56.7389 rounded to 2 d.p. = 56.74

  2. Rounding Off to Significant Figures (s.f.)

    • Example: 0.007856 rounded to 3 s.f. = 0.00786

  3. Rounding Off to the Nearest Whole Number

    • Example: 4.6 rounded to the nearest whole number = 5

  4. Rounding to the Nearest Tenth, Hundredth, and Thousandth

    • Example: 473.765 rounded to the nearest hundredth = 473.77

Evaluation (15 Fill-in-the-Blank Questions)

Choose the correct answer from a, b, c, or d.

  1. 43.678 rounded to 2 decimal places is ____.
    a) 43.68 b) 43.67 c) 43.6 d) 43.70
  2. 0.004527 rounded to 2 significant figures is ____.
    a) 0.0045 b) 0.00453 c) 0.0046 d) 0.00452
  3. 37.95 rounded to the nearest whole number is ____.
    a) 37 b) 38 c) 39 d) 36
  4. The first significant figure in 0.00897 is ____.
    a) 8 b) 9 c) 7 d) 0
  5. 1234.567 rounded to 3 decimal places is ____.
    a) 1234.57 b) 1234.567 c) 1234.568 d) 1234.56
  6. 0.000893 rounded to 2 significant figures is ____.
    a) 0.00089 b) 0.00090 c) 0.00088 d) 0.00089
  7. 3.456 rounded to 1 decimal place is ____.
    a) 3.5 b) 3.4 c) 3.6 d) 3.46
  8. 92.678 rounded to 2 decimal places is ____.
    a) 92.67 b) 92.68 c) 92.6 d) 92.70
  9. 8.499 rounded to the nearest whole number is ____.
    a) 8 b) 9 c) 10 d) 8.5
  10. 0.005637 rounded to 2 significant figures is ____.
    a) 0.0056 b) 0.00564 c) 0.0057 d) 0.00563
  11. 79.345 rounded to 1 decimal place is ____.
    a) 79.4 b) 79.3 c) 79.35 d) 79.5
  12. 567.987 rounded to the nearest hundred is ____.
    a) 600 b) 568 c) 570 d) 567.99
  13. 0.000823 rounded to 3 significant figures is ____.
    a) 0.00082 b) 0.000823 c) 0.000824 d) 0.00083
  14. 99.999 rounded to the nearest integer is ____.
    a) 99 b) 100 c) 101 d) 99.9
  15. 67.445 rounded to 2 decimal places is ____.
    a) 67.45 b) 67.44 c) 67.5 d) 67.40

Class Activity Discussion (15 FAQs with Answers)

  1. What is approximation?

    • It is rounding numbers for easier calculations.

  2. How do I round to a decimal place?

    • Check the digit after the required decimal place.

  3. Why do we round numbers?

    • To make calculations faster and easier.

  4. What is a significant figure?

    • The first non-zero digit and the digits that follow.

  5. What is rounding to the nearest whole number?

    • Converting a decimal number to the closest integer.

  6. How do I round off to the nearest tenth?

    • Look at the hundredths place and decide whether to round up or down.

  7. What does 1 decimal place mean?

    • It means keeping only one digit after the decimal point.

  8. How do you round to 3 significant figures?

    • Keep the first three non-zero digits and round the rest.

  9. Why is approximation important in real life?

    • It simplifies calculations in shopping, banking, and measurements.

  10. What is the rule for rounding numbers?

  • If the next digit is 5 or more, round up; if less than 5, round down.
  1. Does rounding change the value of a number?
  • Yes, but only slightly for easier calculations.
  1. How do you round 98.567 to 2 decimal places?
  • 98.57
  1. What is the difference between decimal places and significant figures?
  • Decimal places count digits after the decimal point, while significant figures count from the first non-zero digit.
  1. How do you round 0.007654 to 3 significant figures?
  • 0.00765
  1. Is 0.000563 in 2 significant figures 0.00056 or 0.00057?
  • 0.00056

 

Presentation Steps

Step 1: Revision of Previous Knowledge

  • The teacher reviews place value and the concept of decimals by asking students to identify digits in different place values.
  • Example: “In the number 345.678, what digit is in the hundredths place?” (Answer: 7).

Step 2: Introduction of the New Topic

  • The teacher writes “Approximation” on the board and explains its meaning with practical examples.
  • Example: “If a shopkeeper tells you a product costs ₦499.99, would you say it costs ₦500?”

Step 3: Student Participation

  • The teacher presents different numbers and asks students to round them to various places.
  • Example: “Round 24.567 to the nearest tenth.” (Students respond: 24.6).

Step 4: Group Work

  • Students work in pairs to round numbers to decimal places, significant figures, and whole numbers.
  • Example: “Round 5.376 to 2 decimal places and 2 significant figures.”

Step 5: Corrections and Clarifications

  • The teacher corrects errors and explains rounding rules again where necessary.

Teacher’s and Learners’ Activities

Activities Teacher’s Role Learners’ Role
Introduction Defines approximation and its uses Listen and respond
Explanation Shows examples of rounding off Observe and ask questions
Classwork Provides numbers for rounding Work in pairs to solve
Review Gives feedback and corrections Participate and take notes

Assessment (10 Short-Answer Questions)

  1. What is the meaning of approximation?
  2. Round 0.004567 to 2 significant figures.
  3. Round 67.894 to 1 decimal place.
  4. What is 845.97 rounded to the nearest whole number?
  5. Identify the first 3 significant figures in 0.009876.
  6. How do you round a number to the nearest tenth?
  7. What is 3.456 rounded to 2 decimal places?
  8. Round 789.654 to the nearest hundred.
  9. Explain the difference between decimal places and significant figures.
  10. Round 0.000879 to 2 significant figures.

Conclusion

  • The teacher summarizes approximation, reinforcing its importance.
  • Students share real-life examples of when they use rounding.
  • The teacher marks students’ work and provides feedback.

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