Lesson Notes By Weeks and Term - Primary 4

WEEK 2
SUBJECT: MATHEMATICS

CLASS: PRIMARY 4

TERM: 3RD TERM

TOPIC: WEIGHT

SUBTOPIC: ADDITION AND SUBTRACTION OF WEIGHT

BEHAVIOURAL OBJECTIVES: At the end of the lesson, pupils should be able to:

1. Solve problems on weights of objects
2. Solve problems on the multiplication of weights in kg and gram
3. Weigh some objects in their classroom environment.

CONTENT

The standard unit of weight is the gram

Remember: 1 000 grams = 1 kilogram

i.e. 1 000 g = 1 kg

The gram is the unit of weight,

and is used to measure very small masses.

Converting kilogram and grams

To convert kilograms to grams, multiply by 1 000.

Examples

1. Convert to grams.
2. 9 kg 2. 1.5 kg 3. 0.048 kg

Solution

1. 9 kg = 9 ×1 000 g = 9 000g
2. 1.5 kg = 1.5 ×1 000 g = 1 500g
3. 0.048 kg = 0.048 ×1 000 g = 48g

B.

Convert to grams.

1. 2kg 350g 2. 3kg 75kg 3. 5kg 8g

Solution

1. 2kg 350g= 2 ×1000g + 350g

=2000+350g

=2350g

2. 3kg 75g= 3 ×1000g + 75g

= 3000g + 75g

= 3075g

3. 5kg 8g= 5×1000g+8g

=5000g+ 8g

=5008g

Exercise 1

Convert each of the following to grams.

1. 4kg 2. 1.25kg 3. 5.504kg 4. 0.75kg 5. 2kg 121g 6. 31\2kg 7. 1kg 567g 8. 71\ 10kg

ADDITION OF WEIGHT IN KILOGRAMS AND GRAMS 

Here 6kg 940g has been added ton2kg 705g.

Solution:

Kg       g

  6       940

+2       705= 8kg    1645  Change 1645 to kg and grams

8kg    1645g=8kg +1kg+645g

       =9kg  645g

245+416g=661g

Exercise 1 

Add the following together.

1. 2kg 371g and 5kg 258g     2. 13kg 107g and 8kg 887      3. 51g 47g and 36kg 69g       4. 53.7kg and 34.85kg   5. 989g and 7kg 918g         6. 26kg 55g and 3kg 69g        7.0.758kg and 0.587kg

SUBTRACTION OF WEIGHT IN KILOGRAMS AND GRAMS

Examples

1. Subtract 2kg 715g from 7kg 875g

Solution: 7kg 875g- 2kg   715g=5kg     124g

2. Subtract 13kg 76gfrom 37kg 161g

Solution:37kg  161g-7kg  875g=24kg  85g

Exercise

Subtract the following.

1.11kg 45g from 16kg 200g      2.5kg 140g from 9kg 345g       3.17.5kg from 20.3kg      4.1.881kg from 2kg

5.0.385kg from 1kg             6.3kg 48g from 5kg

Word problems involving addition and subtraction

Example     

Mrs. Adoh has 567.5kg of beans in her shop. She sold 273.75kg. What weight of beans does she have left?kg

Weight of beans in the shop   =    567.50

Weight of beans sold                = –273.75

 Weight of beans left                 =   293.75

Exercise

Solve the following word problems.

1. The weight of a bucket filled with water is 7.25kg. If the weight of the bucket is 1.75kg,

What is the weight of the water?

2 Take away 15.38kg from 73.4kg.

3. Take away 2.145kg from 2.645kg.
4. What is 5kg minus 3.257kg.

5.Comfort bought 15kg 250g of yam flour. She used 12kg 800g for a feast. What quantity of flour does she have left?

6.Adeoye weighs 2.235kg less than Bolaji. If Bolaji weighs 84.0kg, find Adeoye’s weight.

7.Sola weighs 63kg 725g and Sulaiman's weight is 67kg 10g. Find their difference in weight.

8 Khadija weighs 29.5kg and Ngozi weighs 31.05kg. Find their difference in weight.

9.The weight of two bags containing yam flour and cassava flour is 9kg 25g. If one of the bags weighs 6kg 70g, what is the weight of the other?

10.The weight of three books is 3.54kg. Two of them weigh 2.6kg. Find the weight of the third book.

Multiplication of weight in kilograms and grams

Study these examples of multiplying weights.

Examples                                  

1. Multiply 3kg 325g by 5

2. 8kg 50g ×6

Solution: Note 1000g = 1kg

1. Kg g

     3        325

×   5              =15kg       1625g.

Change 1625g t0 1g 625g

15kg + 1g + 625g

=16kg   625g

2. kg g

        8    50

        ×       6     = 48kg     300g

Solve the following.

1. 30kg 170g ×9         2. 12kg 56g ×4    3. 52kg 80g ×15       4. 31kg 855g ×12

Division of weight in kilograms and grams

Study these examples of dividing weights.

Examples

1. Divide 33 kg 720 g by 6 2. 25 kg 376 g ÷ 8 3. 23.049 kg ÷ 9

1. 5 kg       620 g

    6       33 kg      720 g

             30 kg/       +3 000 g/

              3 kg          3 720 g

                                – 36/

                                        120

                                      –120/

                                            00

Thus 33 kg 720 g ÷ 6 = 5 kg 620 g

2. 3 kg 172 g                      

8    25 kg    376 g

     24 kg     +1 000 g/

     1 kg        1 376 g

                        – 8̅̅̅̅̅̅/

                        57

                      – 56/

                            16

                             – 16\00

Thus 25 kg 376 g ÷ 8 = 3 kg 172 g

         2.561 kg/

9       23.049 kg

        – 18/

           50

        – 45/

           54

        – 54/

           09

         – 09/

            00

Thus 23.049 kg ÷ 9 = 2.561 kg

Exercise

1. Divide 12 kg 260 g by 4 2. Divide 5 kg 200 g by 4 3. Divide 6 kg 360 g by 5
2. Divide 10 kg 260 g by 6 5. Divide 7 kg 263 g by 3 6. Divide 15 kg 366 g by 6
3. Divide 10 kg 989 g by 9 8. 41.976 kg ÷ 4 9. 17.152 kg ÷ 8
4. 21.315 kg ÷ 5

Unit 7

Word problems involving multiplication and division

Examples

1. A bag of cement weighs 50 kg. What is the total weight of 4 bags of cement?

Solution

              kg

              50

              × 4

             200 kg

The total weight of 4 bags of cement is 200 kg.

2. Five women share 14.5 kg of maize equally. How much will each get?

Solution

     2.9 kg

 14.5 kg/5

      – 10/

        45

      – 45/

        00

" Each woman will get 2.9 kg of maize

Exercise

1. Four cartons of soft drinks weigh 15 kg 316 g. How much will one carton weigh?
2. Find the total weight of 8 tins of paint if each weighs 1.75 kg.
3. A pair of shoes weighs 875 g. Find the weight of 12 similar pairs of shoes.
4. A sachet of gari weighs 255 g. Find the weight of 15 similar sachets of gari.
5. Eight women are to share 35 kg 232 g of rice equally among themselves. How much

does each woman get?

6. A man carried 5 bags of sand from one place to another. Each bag weighs 24.75 kg.

Find the total weight of sand carried by the man.

7. Find the weight of 14 concrete blocks if each weighs 14 kg.
8. 1 kg 449 g of powdered milk is shared among 9 pupils. How much will each receive?
9. Multiply 5 kg 37 g by 8.
10. Divide 123 kg 750 g by 18.

 Exercise

1. Convert 3 kg 356 g to grams only. 2. Convert 0.84 kg to grams.
2. Convert 1 17

50 kg to grams. 4. Convert 2 045 g to kilograms only.

5. Convert 3 124 g to kilograms and grams. 6. Add 5 kg 495 g to 2 kg 705 g.
6. 1.785 kg to 0.578 kg. 8. Subtract 3 kg 715 g from 7 kg 875 g.
7. What is 5 kg 297 g from 2 kg 775 g? 10. Solve 2 kg × 5.
8. 5.35 kg × 4. 12. Divide 63 kg 720 g by 6.
9. Divide 18 kg 198 g by 9. 14. Multiply 5 kg 39 g × 8.
10. The weight of 7 crates of mineral is 10.5 kg. What is the weight of one?