Decimal Fractions : Addition, Subtraction and Conversion of Decimals

SECOND TERM E-NOTES FOR PRIMARY 4 MATHEMATICS

SUBJECT: Mathematics
CLASS: Basic Four / Primary 4
WEEK: 3
TOPIC: Decimal Fractions: Addition and Subtraction of Decimals

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IMPORTANCE OF TOPIC

1. Helps in calculating with accuracy in weight, money, and distance.
2. Aids in recording and analyzing results in sports and other activities.

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LEARNING OBJECTIVES

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

1. Identify decimal fractions up to tenths, hundredths, and thousandths.
2. Convert fractions into decimals.
3. Perform addition and subtraction of decimals accurately.
4. Solve real-life problems involving decimal operations.

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LEARNING ACTIVITIES

1. Pupils will work in small groups to design a quarter-circle (0.25) using cardboard.
2. Pupils will practice aligning decimal points for addition and subtraction exercises.
3. Pupils will solve word problems involving decimals to enhance understanding.

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EMBEDDED CORE SKILLS

• Critical thinking and problem-solving.
• Communication and collaboration.
• Creativity and imagination.
• Leadership and personal development.

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LEARNING MATERIALS

• Cardboard
• Marker pens
• Scissors
• Record of time in sports events

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CONTENT

What Are Decimal Fractions?

Decimal fractions express parts of a whole using a base-ten place value system.

• Examples:
  • 0.5 = 5/10
  • 0.25 = 25/100

Decimal numbers are written with a decimal point separating whole numbers and fractional parts.
For instance:

• 2.34 = 2 + 34/100

Addition of Decimals

To add decimals:

1. Align the decimal points.
2. Add as you would whole numbers.
3. Place the decimal point in the result.
   Example:

• 1.25 + 0.75 = 2.00

Subtraction of Decimals

To subtract decimals:

1. Align the decimal points.
2. Borrow where necessary.
3. Subtract as with whole numbers.
   Example:

• 3.50 – 1.25 = 2.25

Identification of Decimal Fractions

Decimal fractions represent parts of a whole:

• Tenths (0.1)
• Hundredths (0.01)
• Thousandths (0.001)

Changing Fractions to Decimals

To convert fractions to decimals, divide the numerator by the denominator.
Examples:

1. 3/4 = 0.75
2. 1/8 = 0.125

Changing Decimals to Fractions

Write the decimal as a fraction based on its place value, then simplify.
Examples:

1. 0.5 = 5/10 = 1/2
2. 0.25 = 25/100 = 1/4

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EVALUATION QUESTIONS

Multiple Choice Questions

1. Which of the following is a decimal fraction?
   a) 1/4
   b) 3/5
   c) 0.5
   d) 2/3
   Answer: c) 0.5
2. What is the decimal representation of 5/8?
   a) 0.375
   b) 0.4
   c) 0.6
   d) 0.625
   Answer: d) 0.625
3. What is the sum of 2.5 and 1.25?
   a) 2.75
   b) 3.25
   c) 3.5
   d) 3.75
   Answer: b) 3.25
4. What is 0.25 as a fraction?
   a) 1/4
   b) 1/2
   c) 2/5
   d) 2/10
   Answer: a) 1/4
5. What is 0.8 as a fraction in simplest form?
   a) 4/5
   b) 8/10
   c) 2/5
   d) 8/100
   Answer: a) 4/5

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CLASS ACTIVITIES

1. Pupils will solve 10 problems involving the addition of decimals.
2. Pupils will collaborate to identify decimal fractions in given numbers.
3. Pupils will convert given fractions into decimals and decimals into fractions.

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CONCLUSION

The teacher will review the steps for adding, subtracting, and converting decimals and fractions. Feedback will be given based on pupils’ classwork and participation.

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ASSESSMENT

1. Add: 4.35 + 2.5 = __________.
   Answer: 6.85
2. Convert 1/3 to a decimal.
   Answer: 0.333…
3. Subtract: 7.6 – 5.25 = __________.
   Answer: 2.35
4. Identify the decimal fraction in 3.42.
   Answer: 0.42
5. Write 0.125 as a fraction in simplest form.
   Answer: 1/8

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