Addition And Subtraction Of Fractions Basic 5 Mathematics Lesson Note

Behavioural Objectives:

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

1. Add and subtract fractions with common denominators
2. Add and subtract fractions with different denominators and mixed fractions
3. Express answers in their simplest forms and lowest terms of fractions
4. Use the LCD method to add and subtract fractions
5. Apply quantitative aptitude problems related to addition and subtraction of mixed numbers

Keywords:

• Fractions
• Mixed numbers
• Decimal fractions
• Addition
• Subtraction
• Real-life problems

Set Induction:

The teacher will start with a discussion on how fractions are used in everyday life, such as cooking or sharing food equally among people, adding and subtracting fractions.

Entry Behaviour:

Pupils should be familiar with basic fractions and simple addition and subtraction.

Learning Resources and Materials:

1. Fraction charts
2. Worksheets for practice
3. Real-life scenarios
4. Whiteboard and markers

Building Background/Connection to Prior Knowledge:

The teacher will review basic fraction operations and introduce the concept of adding and subtracting fractions.

Embedded Core Skills:

• Problem solving
• Analytical thinking
• Application of mathematical operations

Learning Materials:

1. Fraction charts
2. Practice worksheets
3. Visual aids

Reference Books:

Lagos State Scheme of Work, Primary 5 Mathematics Textbook

Instructional Materials:

1. Charts
2. Worksheets
3. Whiteboard and markers

Content:

1. Addition and Subtraction of Mixed Numbers

• Adding fractions with common denominators
• Adding mixed numbers
• Subtracting fractions

2. Subtraction of Fractions and Mixed Numbers

• Subtracting fractions with common denominators
• Subtracting mixed numbers
• Converting and practice problems

3. Addition and Subtraction of Decimal Fractions

• Adding decimal fractions
• Subtracting decimal fractions

4. Real Life Problems

• Practical problems with subtraction of fractions to real life situations
• Application problems

5. Quantitative Reasoning

• Solving quantitative aptitude problems involving fractions and mixed numbers
• Practice problems and examples

Addition of Fractions and Mixed Numbers

Adding Fractions with Common Denominators:

To add fractions with the same denominators, add the numerators and add the denominators.

Formula: a/c + b/c = (a + b)/c

Examples:

• 1/5 + 2/5 = 3/5
• 2/7 + 3/7 = 5/7 (which simplifies to 5/7)
• 3/8 + 1/8 = 4/8 (which simplifies to 1/2)
• 4/9 + 2/9 = 6/9 (which simplifies to 2/3)
• 5/12 + 7/12 = 12/12 = 1

Adding Mixed Numbers:

Add the whole numbers together and then add the fractions. If needed, convert any improper fractions to mixed numbers.

Examples:

• 2 1/3 + 1 1/3 = 3 2/3
• 1 3/4 + 2 1/4 = 3 4/4 = 4
• 3 2/5 + 1 3/5 = 4 5/5 = 5
• 2 3/7 + 1 4/7 = 3 7/7 = 4
• 1 5/8 + 2 1/8 = 3 6/8 = 3 3/4

Class Work:

• 3/7 + 2/7 = ?
• 2 1/5 + 3 2/5 = ?
• 1/6 + 4/6 = ?
• 1 3/8 + 2 1/8 = ?
• 7/12 + 4/12 = ?

Subtraction of Fractions and Mixed Numbers

Subtracting Fractions with Common Denominators:

To subtract fractions with the same denominators, keep the denominators and subtract the numerators.

Formula: a/c – b/c = (a – b)/c

Examples:

• 7/8 – 3/8 = 4/8 (which simplifies to 1/2)
• 5/6 – 1/6 = 4/6 (which simplifies to 2/3)
• 9/10 – 3/10 = 6/10 (which simplifies to 3/5)
• 11/12 – 5/12 = 6/12 (which simplifies to 1/2)
• 8/9 – 2/9 = 6/9 (which simplifies to 2/3)

Subtracting Mixed Numbers:

Subtract the whole numbers and then subtract the fractions. Borrow from the whole number if needed.

Examples:

• 3 4/5 – 1 2/5 = 2 2/5
• 5 7/8 – 2 3/8 = 3 4/8 = 3 1/2
• 4 5/6 – 1 1/6 = 3 4/6 = 3 2/3
• 6 3/4 – 2 1/4 = 4 2/4 = 4 1/2
• 5 9/11 – 2 3/11 = 3 6/11 (which simplifies to 3 6/11)

Class Work:

• 7/9 – 4/9 = ?
• 3 5/6 – 1 2/6 = ?
• 11/12 – 5/12 = ?
• 4 7/8 – 2 3/8 = ?
• 8/10 – 3/10 = ?

Addition and Subtraction of Decimal Fractions

Adding and Subtracting Decimals:

Align the decimal points and add or subtract as you would with whole numbers. Place the decimal point in the result.

Examples:

• 3.4 + 2.5 = 5.9
• 7.8 + 1.3 = 9.1
• 6.25 + 3.75 = 10.0
• 4.6 + 2.8 = 7.4
• 5.7 + 3.4 = 9.1

Class Work:

• 2.3 + 4.6 = ?
• 5.8 + 2.7 = ?
• 8.4 – 3.2 = ?
• 9.6 – 4.5 = ?
• 7.25 + 2.75 = ?

Real-Life Problems

Solving Addition and Subtraction of Fractions in Real Life Situations:

Apply fractions to everyday scenarios.

Examples:

Example 1: John ate 1/4 of a cake and Jane ate 1/3 cup. How much cake is left?

• Solution: 1/4 + 1/3 = 3/12 + 4/12 = 7/12. So 1 – 7/12 = 5/12 of the cake is left.

Example 2: A piece was delivered as 3/4 water and 1/5 milk. How much pure is left?

• Solution: 3/4 + 1/5 = 15/20 + 4/20 = 19/20. So 1 – 19/20 = 1/20 pure is left.

Example 3: Mary bought 2 1/3 meters of cloth. She used 1 1/4 meters to make a dress. How much cloth is left?

• Solution: 2 1/3 – 1 1/4 = 2 4/12 – 1 3/12 = 1 1/12 meters.

Example 4: A bag used 3/8 of a piece of ribbon for one gift and uses 1/4 more how much gift did she use?

• Solution: 3/8 + 1/4 = 3/8 + 2/8 = 5/8

Example 5: John’s farm received 2 3/4 inches of rain in week one and 1 5/8 inches in week two. How much rain altogether?

• Solution: 2 3/4 + 1 5/8 = 2 6/8 + 1 5/8 = 3 11/8 = 4 3/8 inches

Example 6: A recipe calls for 1 3/4 cups of flour and 2/3 cup of sugar. How much more flour than sugar does the recipe require?

• Solution: 1 3/4 – 2/3 = 1 9/12 – 8/12 = 1 1/12 cups

Example 7: Susan had 3 1/2 hours to finish her project. She has already spent 1 3/4 hours. How much time is left?

• Solution: 3 1/2 – 1 3/4 = 3 2/4 – 1 3/4 = 1 3/4 hours (borrowing: 2 6/4 – 1 3/4 = 1 3/4)