Ratio & Proportion Class 6 PPT

 Page 1


Chapter-XII
Ratios and Proportions
Page 2


Chapter-XII
Ratios and Proportions
Introduction
? We normally compare two quantities by taking the 
difference between them.
? But most often this does not work out well.
? For such cases we use what is called a ratio.
Page 3


Chapter-XII
Ratios and Proportions
Introduction
? We normally compare two quantities by taking the 
difference between them.
? But most often this does not work out well.
? For such cases we use what is called a ratio.
What is a Ratio ?
? A ratio is a comparison between similar quantities using 
division.
? Note that for using ratio, the quantities need to be 
similar.
? We represent a ratio of two quantities say ‘a’ and ‘b’ by         
a : b = a / b . 
Page 4


Chapter-XII
Ratios and Proportions
Introduction
? We normally compare two quantities by taking the 
difference between them.
? But most often this does not work out well.
? For such cases we use what is called a ratio.
What is a Ratio ?
? A ratio is a comparison between similar quantities using 
division.
? Note that for using ratio, the quantities need to be 
similar.
? We represent a ratio of two quantities say ‘a’ and ‘b’ by         
a : b = a / b . 
Example 
? For example, if Ramesh scores 80 marks in an exam and 
Suresh scores 60 marks, then the ratio of their marks is 
80:60=80/60=4/3=4:3.
? Thus we see that two different ratios can be equal, for 
example in the above 80:60=4:3 . Hence they can be taken 
as a sort of equal measures . 
? In a ratio, the ordering is important. Thus 3:4 is different 
from 4:3. Compare these to division. Is ¾ = 4/3 ? No. And 
hence the same in case of ratios. 
Page 5


Chapter-XII
Ratios and Proportions
Introduction
? We normally compare two quantities by taking the 
difference between them.
? But most often this does not work out well.
? For such cases we use what is called a ratio.
What is a Ratio ?
? A ratio is a comparison between similar quantities using 
division.
? Note that for using ratio, the quantities need to be 
similar.
? We represent a ratio of two quantities say ‘a’ and ‘b’ by         
a : b = a / b . 
Example 
? For example, if Ramesh scores 80 marks in an exam and 
Suresh scores 60 marks, then the ratio of their marks is 
80:60=80/60=4/3=4:3.
? Thus we see that two different ratios can be equal, for 
example in the above 80:60=4:3 . Hence they can be taken 
as a sort of equal measures . 
? In a ratio, the ordering is important. Thus 3:4 is different 
from 4:3. Compare these to division. Is ¾ = 4/3 ? No. And 
hence the same in case of ratios. 
Proportions 
? We can also compare two ratios. We do so by using 
proportions.
? If two ratios are the same then we say that they are in 
proportion.
? We denote a proportion by ::. Thus if ‘a : b = c : d’ , then    
‘a : b :: c : d’ . 
? As in a ratio, so also in a proportion the ordering of the 
numbers is important.