Math > Year 3

Measuring & Comparing Mass

Mass: It is defined as a measurement of how heavy or how light something is.


How to measure the mass of an object? 

We can use a weighing machine to measure the mass of an object.
 


 


Units of mass

Mass can be measured in kilograms and grams.


 


 

1kg = 1,000g

 

Estimation of weight using balances scale:
 


 

The pan with stone is downwards, which means the stone is heavier and the pan with the leaf is upwards, which means the leaf is lighter in weight.

So, we can say that the leaf has less weight than the stone.
 

 


 

The scales are balanced, which means the apple and the burger are of the same mass. 

 

How to measure the weight of objects using a measuring scale? 
 

Weight in kilograms:

 


 

We can see that the red indicator is pointing at 4 kg.

It means the weight of the pumpkin is 4 kg. 


Weight in grams:
 


 

We can see the indicator is pointing at 125g.
Therefore, the weight of the apple is 125g.


 

How can we compare the masses of different objects having different units?  
 


 




To compare the masses with different units, we need to make the units the same.
 

Examples:
 

1. Compare the following. 
 


 

Weight of butter = 25g

Weight of pumpkin = 4 kg

We know that 1 kg = 1,000 g

That means 4 kg = 4,000 g

25 g < 4,000 g

Weight of butter < Weight of pumpkin
 



 

2. Put the correct symbol to compare the masses.
 


 

Weight of the toy bus = 1,000 g

Weight of the toy train = 1 kg

We know that 1,000 g = 1 kg

Therefore the weight of the toy bus and the toy train is the same. 

We will put an equal sign to show that both the masses are equal.



 

 

Let’s try some  questions:
 

 

Question 1: Weight of stone is  _________ the weight of a can.




 

The pan with the stone is downwards, which means the stone is heavier and the pan with the can is upwards, which means the can is lighter in weight.

So, we can say that a stone has a weight greater than the weight of a can.


 

Question 2: The weight of the oranges is ______.
 


 

Explanation:

The arrow is pointing towards 300g. That means the weight of the oranges is 300g.


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