# Estimation – Round Whole And Decimal Numbers, Sum, Difference and Product of Estimated Whole and Decimal Numbers (Primary 4)

Last Updated on July 16, 2020 by Alabi M. S.

MATHEMATICS

SECOND TERM

WEEK 6

PRIMARY 4

THEME – BASIC OPERATIONS

PREVIOUS LESSON – Second Term Scheme of Work and Plan Lesson Notes for MATHEMATICS Week 1 to Week 12 Primary Schools

TOPIC – ESTIMATION

LEARNING AREA

1. Round Whole Numbers to 10 and 100

2. Round Decimal Numbers to the Nearest Whole Numbers

3. Sum and Difference of Estimated Numbers

PERFORMANCE OBJECTIVES

By the end of the lesson, the pupils should have attained the following objectives (cognitive, affective and psychomotor) and should be able to –

1. round whole numbers to the nearest 10, 100.

2. round decimals to the nearest whole numbers.

3. estimate the sums and differences of whole numbers and decimals.

4. estimate the product of two numbers solve word problems involving estimation.

ENTRY BEHAVIOUR

INSTRUCTIONAL MATERIALS

The teacher will teach the lesson with the aid of charts on estimates

METHOD OF TEACHING – Choose a suitable and appropriate methods for the lessons.

Note – Irrespective of choosing methods of teaching, always introduce an activities that will arouse pupil’s interest or lead them to the lessons.

REFERENCE MATERIALS

1. Scheme of Work

2. 9 – Years Basic Education Curriculum

3. Course Book

4. All Relevant Material

5. Online Information

CONTENT OF THE LESSON

LESSON ONE – INTRODUCTION

Pupil’s Activities 1 – Rounding to the nearest 10 Teacher’s remark – 10 20 30 40 50 60 70 80 90. Each of these numbers are multiples of 10 and each number has zero in its unit place. These numbers (i.e. multiples of 10) are round numbers. 11 12 13 14 15 16 17 18 19 21 24 25 etc These numbers are called non rounded because the digits in the unit place is greater than zero. Non rounded numbers can be replaced by the nearest multiples of 10, 100. This is called rounding. The middle number is greater than 22 (2 < 5)

22 is nearer to 20 than to 30,

Therefore, 22 is rounded to 20 to the nearest 10.

25 is halfway (middle number) between 20 and 30.

Therefore, T25 is rounded to 30 to the nearest 10.

Pupil’s Activities 2 – Exercise/Take Home

Round these Numbers to the Nearest 10

1. 12

2. 86

3. 79

4. 64

5. 36

LESSON TWO – ROUNDING TO THE NEAREST 100

Pupil’s Activities 1 Teacher’s remark – 783 is nearer to 800 than to 700. Therefore, 783 is rounded to 800 to the nearest 100. Pupil’s Activities 2 – Exercise/Take Home

Round these numbers to the nearest 100.

1. 373

2. 450

3. 213

4. 731

5. 582

LESSON THREE – ROUNDING DECIMALS TO NEAREST WHOLE NUMBERS

Teacher’s/Pupil’s Activities 1 Teacher’s remark – Decimals can also be rounded to the nearest whole numbers with and without using a number line. 1.51 is halfway (middle number) between 1 and 2. 1.51 is rounded to 2 to the nearest whole number.

Pupil’s Activities 2 – Working Examples

Round to the nearest whole number.

1. 19.5

19.5 is middle number between 10 and 20.

Therefore, rounded to 20.

2. 6.2

6.2 is close 6 than 7.

Therefore, rounded to 6.

3. 4.98

4.98 is close to 5 than 4.

Therefore, rounded to 5.

Pupil’s Activities 3 – Exercise/Take Home

Round these to the nearest whole number.

1. 3.82

2. 5.83

3. 2.88

4. 3.29

5. 7.8

LESSON FOUR – ESTIMATING SUMS AND DIFFERENCES OF WHOLE NUMBERS

Teacher’s/Pupil’s Activities 1 – Estimating Sum of Whole Numbers

Working Examples

1. 57 + 63

6  7 ~  7  0 (nearest 10)

6  3 ~  6  0 (nearest 10)

————-

13 0 ~ 130

The difference is 0.

2. 590 + 428

5 9 0 ~ 6 0 0 (nearest 100)

1 3 0 ~ 1 0 0 (nearest 100)

—————

7 2 0 ~ 7 0 0

The difference is 20.

Teacher’s/Pupil’s Activities 2 – Estimating Difference of Whole Numbers

Working Examples

1. 76 – 46

7  6 ~ 8 0 (nearest 10)

4  6 ~ 5 0 (nearest 10)

————

3 0 ~ 3 0

The difference is 0.

2. 858 – 536

8 5 8 ~ 9 0 0 (nearest 100)

5 3 6 ~ 5 0 0 — (nearest 100)

___________

3 2 2 ~ 4 0 0

The difference is 78.

Pupil’s Activities 3 – Exercise/Take Home

Estimate the following.

1. 97 + 39

2. 82 – 47

3. 402 — 195

4. 389 + 924

LESSON FIVE – ESTIMATING SUMS AND DIFFERENCES OF DECIMAL NUMBERS

Teacher’s/Pupil’s Activities 1 – Estimate Sum

Estimate the following to the nearest whole number and simplify.

1. 2.95 + 2.07

2.95 ~ 3. (nearest whole numbers)

2.07 ~ 2 + (nearest whole numbers)

________

5.02 ~ 5

The difference is 0.02.

2. 30.2 + 18.9

30.2 ~ 30 (nearest whole numbers)

18.9 ~ 20 (nearest whole numbers)

_________

49.1 ~ 50

The difference 0.9.

Teacher’s/Pupil’s Activities 2 – Estimate Difference

Working Examples

3. 25.9 — 13.5

25.9 ~ 30

13.5 ~ 14

________

12.4 ~ 16

4. 3.89 — 2.49

3.89 ~ 4

2.49 ~ 2

_______

2.40 ~ 2

Pupil’s Activities 3 – Exercise/Take Home

Estimate the following to the nearest whole number and simplify.

1. 21.97 + 36.48

2. 7.76 + 4.9

3. 41.97 — 36.46

4. 7.76 — 4.90

LESSON SIX – EXTRA CLASSES/QUANTITATIVE REASONING

Extra Class – Estimating the product of two numbers. Follow the same procedure.

Quantitative Reasoning – As stated in the pupil’s quantitative books or textbooks.

PRESENTATION

To deliver the lesson, the teacher adopts the following steps:

1. To introduce the lesson, the teacher revises the previous lesson. Based on this, he/she asks the pupils some questions;

2. Guides pupils to find estimate of sum and product of numbers.

Pupil’s Activities – Estimate sums and products of numbers.

CONCLUSION

To conclude the lesson for the week, the teacher revises the entire lesson and links it to the following week’s lesson.

LESSON EVALUATION

Pupils to:

1.  estimate the sum and product of numbers, heights, lengths and widths within and outside the school.

2. carry out estimate involving sum and product of numbers.