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Father gave them some idea of the weight of each thing.
Thing loaded  Weight 
A sack of wheat  100 kg 
A sack of rice  35 kg 
Water tank  50 kg 
Almirah  70 kg 
A table  10 kg 
A chair  5 kg 
A mattress  20 kg 
Bamboo ladder  10 kg 
Pots and pans  10 kg 
Solution:
Now you also make your own balance. Write down how you made it. Also draw a picture of your balance in the box below.
Solution:
Disclaimer: The answer may vary from student to student based on his/her observation. It is highly recommended that students prepare the answer on their own.
Activity
Mannu and Jaiju put a pencil and a geometry box in the two pans of the balance. Which pan will go down? Why? Draw a picture to show it.
Solution:
The pan with the geometry box will go down because the geometry box is heavier than the pencil.
What is heavier?
Make pairs of different things and use the balance to decide which is heavier. First guess which thing will take the pan down and then check with your balance.
Solution:
Disclaimer: The purpose of this section is to make the students observe their surroundings. The answer may vary from student to student based on his/her experience. It is highly recommended that the students prepare the answer on their own.
What is the heaviest?
Make groups of three things. For example ― eraser, ball and paper. Use the balance to arrange them in order of weight – the lightest, the one with in–between weight, the heaviest. Complete the table with at least five example.
Lightest  Inbetween weight  Heaviest 
Paper  Eraser  Ball 
Solution:
Lightest  Inbetween weight  Heaviest 
Paper 
Eraser 
Ball 
Handkerchief 
Scarf 
Shawl 
Grape 
Date 
Potato 
Orange 
Coconut 
Pumpkin 
Groundnut

Lemon 
Papaya 
Practice Time
• Which pan of the balance will go down? Show by drawing an arrow.
• Is the weight on any of the pans equal to 1 kilogram? Mark it.
• How many grams are there in 1 kg?
Solution:
Grams and Kilograms
Name 5 things that we usually buy —
In grams  In kilograms 
1.  1. 
2.  2. 
3.  3. 
4.  4. 
5.  5. 
Solution:
In grams  In kilograms 
1. Pomegranate powder  1. Vegetables 
2. Turmeric powder  2. Fruits 
3. Colgate powder  3. Sugar 
4. Soap bar  4. Rice 
5. Chilli powder  5. Wheat 
Guess and write the weight of each thing he bought—in g or kg.
Items  Weight 
Rice  5 
Sugar  1 
Mustard seeds  10 
Wheat  3 
Dal  500 
Tea  250 
Pepper  25 
Solution:
Items  Weight 
Rice  5 kg 
Sugar  1 kg 
Mustard seeds  10 g 
Wheat  3 kg 
Dal  500 g 
Tea  250 g 
Pepper  25 g 
Now you show how Abdu will use these stone pieces to weigh —
(a) 4 kg of firewood
(b) 3 kg of firewood
(c) 7 kg of firewood
Solution:
(a)
Abdu will put the firewood in one of the pans of the balance and the 6 kg stone in the other.
The pan with the stone will go down. Abdu will then put the 2 kg stone on the firewood and both the pans will become balanced.
Thus, Abdu will use 2 kg and 6 kg stones to weigh 4 kg of firewood.
(b)
Abdu will put the firewood in one of the pans of the balance and the 5 kg stone in the other.
The pan with the stone will go down. Abdu will then put the 2 kg stone on the firewood and both the pans will become balanced.
Thus, Abdu will use 2 kg and 5 kg stones to weigh 3 kg of firewood.
(c)
Abdu will put the firewood in one of the pans of the balance and the 5 kg stone in the other.
The pan with the firewood will go down. Abdu will then put the 2 kg stone in the pan with the 5 kg stone. Now, both the pans will become balanced.
Thus, Abdu will use 2 kg and 5 kg stones to weigh 7 kg of firewood.
Post Office
Have you ever been to a post office? __________
What different things do people go there for?
How much does a postcard cost? __________
How much does an inland letter cost? __________
Solution:
Look at the postal rates given in the chart.
1. How much will you have to pay for stamps on a letter weighing 50 grams? ___________
2. Akash wants to send a parcel of the Math Magic textbook to his friend Rani in Chennai. The book weighs 200 g. See the chart to find the cost of posting the book. __________
Solution:
1.
Weight of a letter = 50 g
Cost of a letter weighing 20 g or less = Rs 5
If the weight of a letter is more than 20 g, then the cost for every additional 20 g is Rs 2.
Now, weight of letter = 50 g
= 20 g + 20 g + 10 g
Total cost paid for the stamps = Rs 5 + Rs 2 + Rs 2
= Rs 9
2.
Cost of a parcel weighing 50 g or less = Rs 5
If the weight of a parcel is more than 50 g, then the cost for every additional 50 g is Rs 3.
Weight of the parcel containing a book = 200 g
= 50 g + 50 g + 50 g + 50 g
Total cost to be paid by Akash = Rs 5 + Rs 3 + Rs 3 + Rs 3
= Rs 14
Thus, Akash has to pay Rs 14 for posting the book.
Read the weight shown in the picture. Find out the cost of sending a parcel of that weight.
Parcel weight = _______
Cost of stamps = _______
Solution:
Weight of the parcel = 230 g
Cost of a parcel weighing 50 g or less = Rs 5
If the weight of the parcel is more than 50 g, then the cost for every additional 50 g is Rs 3.
Now, weight of the parcel = 230 g
= 50 g + 50 g + 50 g + 50 g + 30 g
∴ Cost of the stamps = Rs 5 + Rs 3 + Rs 3 + Rs 3 + Rs 3
= Rs 17
So, the total cost of sending the parcel of 230 g is Rs 17.
Parcel weight = 230 g
Cost of stamps = Rs 17
How Many Stamps?
• Rahul needs stamps of Rupees 25 for his parcel. He went to the post office. Only stamps of Re 1, Rs 2, Rs 5 and Rs 10 were there at that time. Using those stamps in how many different ways can he make Rs 25?
• Can you show five different ways? What is the heaviest parcel he can send using stamps of Rs 25?
Solution:
The 5 different ways are given below:
(1)
Rahul can buy five stamps of Rs 5 each in order to buy stamps of Rs 25 for his parcel.
Cost of 1 stamp = Rs 5
Cost of 5 stamps = Rs 5 × 5
= Rs 25
(2)
Rahul can buy two stamps of Rs 10 each and one stamp of Rs 5 in order to buy stamps of Rs 25 for his parcel.
Cost of two stamps of Rs 10 each = Rs 10 × 2
= Rs 20
Total cost of two stamps of Rs 10 each and one stamp of Rs 5 = Rs 20 + Rs 5
= Rs 25
(3)
Rahul can buy ten stamps of Rs 2 each and one stamp of Rs 5 in order to buy stamps of Rs 25 for his parcel.
Cost of ten stamps of Rs 2 each = Rs 2 × 10
= Rs 20
Total cost of ten stamps of Rs 2 each and one stamp of Rs 5 = Rs 20 + Rs 5
= Rs 25
(4)
Rahul can buy three stamps of Rs 5 each and five stamps of Rs 2 each in order to buy stamps of Rs 25 for his parcel.
Cost of three stamps of Rs 5 each = Rs 5 × 3
= Rs 15
Cost of five stamps of Rs 2 each = Rs 2 × 5
= Rs 10
Total cost of three stamps of Rs 5 each and five stamps of Rs 2 each = Rs 15 + Rs 10
= Rs 25
(5)
Rahul can buy three stamps of Rs 5 each and one stamp of Rs 10 in order to buy stamps of Rs 25 for his parcel.
Cost of three stamps of Rs 5 each = Rs 5 × 3
= Rs 15
Total cost of three stamps of Rs 5 each and one stamp of Rs 10 = Rs 15 + Rs 10
= Rs 25
Our Weight Together
A frog was struggling to escape from the mouth of a crow. How can I escape? — the frog thought. Suddenly a trick came to his mind. He asked the crow — Are you good at arithmetic? If yes, then I will ask you a problem.
Your weight is 650 g and I am only 145 g. How much do we weigh together?
The crow was good at mathematics, so he sappily opened his beak to answer.
What happened after that? So what was the answer the crow wanted to give? ___________
Solution:
Weight of the crow = 650 g
Weight of the frog = 145 g
Total weight of the crow and the frog = 650 g + 145 g
= 795 g
Working:
$\begin{array}{cccc}& 6& 5& 0\\ +& 1& 4& 5\\ & 7& 9& 5\\ & & & \end{array}$
The crow calculated the total weight as 795 g and when he opened his mouth to answer, the frog escaped from his mouth.
Now, you also fill the table by finding out the age, height and weight of any five friends.
Name  Age  Height  Weight 
Solution:
Name  Age  Height  Weight 
Akshay  10 years  130 cm  40 kg 
Varun  11 years  135 cm  42 kg 
Ankita  9 years  120 cm  38 kg 
Shikhar  9 years  125 cm  37 kg 
Pooja  11 years  130 cm  35 kg 
How Many Oranges?
All oranges have equal weight. The two papayas have the same weight. The weights in the first and second balances are equal.
How many oranges balance the weight in the third?
Solution:
In the first balance, we see that the total of weight of 3 oranges is equal to the combined weights of an orange and a mango. As all the oranges are of the same weight, we can say that the weight of a mango is equal to the weight of 2 oranges.
In the second balance, we see that the total weight of 2 papayas is equal to the combined weights of 2 oranges and a mango. But as two oranges and a mango weigh the same, we can say that the weight of 2 papayas is equal to the weight of 2 mangoes. Thus, the weight of each papaya is equal to the weight of each mango and the weight of a mango is equal to the weight of 2 oranges. Therefore in the third balance, we need 4 oranges on the right pan of the balance in order to have equal weights on both the sides.
Find That Marble
There are 3 marbles of the same size but one marble is slightly heavier or lighter than the other two. Can you find which is that marble and if it is heavier or lighter? You can use a balance only two times.
Solution:
Suppose we have three marbles, A, B and C, such that one of them is slightly heavier or lighter than the other two. Let us first put marbles A and B in two different pans. We will get the following situations:
(1) If the two pans balance each other, then marble C is either heavier or lighter than the other two marbles. To check this, let us put marbles A and C in the two different pans. If the pan containing marble C goes down, then we can say that marble C is heavier than marbles A and B. If the pan containing marble A goes down, then we can say that marble C is lighter than marbles A and B.
(2) Suppose the two pans containing marbles A and B do not balance each other. Let the weight of marble A be less than that of marble B. Now, let us remove marble B from the pan and put marble C in its place. After this, let us compare the weights of marbles A and C. If the two pans balance each other, then we can say that marble B is heavier than marbles A and C. If the pan containing marble C goes down, then we can say that the weights of marbles B and C are equal and marble A is lighter than marbles B and C.