Suppose I have 10 rupees

1.jpg

& Sanjay has 30 rupees

2.jpg

I can say,

  Sanjay has 20 rupees more than me

And I can also say,

  Sanjay has 3 times as much money than me

 

While writing 3 times,

I divided Sanjay’s money to my money

  (Sanjay^′ s Money)/(My Money) = 30/10

= 3/1

Here 3/1 is ratio

We also write is as 3 : 1

 

Let’s take some more examples

Suppose I have 10 kg mangoes, 5 kg apples & 5 kg oranges.

3.jpg

 

What is ratio of weight of mangoes to weight of apples:-

 

Dividing weight of mangoes

by weight of apple

  • (Weight of mangoes)/(Weight of apple) = (10 kg)/(5 kg)
  • = 10/5
  • = 2/1
  • Hence, 2/1 or 2 : 1 is the ratio

4.jpg

 

Ratio of weight of apples and weight of oranges :-

Dividing weight of apples

by weight of orange

5.jpg

(Weight of apple)/(Weight of oranges) = (5 kg)/(5 kg)

   = 5/5

   = 1/1

Hence, 1/1 or 1 : 1 is the ratio

 

Ratio of weight of oranges and weight of mangoes :-

Dividing weight of oranges

by weight of mangoes

5.jpg

(Weight of oranges)/(Weight of mangoes) = (5 kg)/(10 kg)

= 5/10

= 1/2

Hence, 1/2 or 1 : 2 is the ratio

Ratio’s can work the opposite way as well

 

Suppose ratio of girls to boys in a class is 1 : 2. And, number of boys is 20. Find number of girls & total number of students.

Given ratio is 1 : 2

i.e.

(Number of girls)/(Number of boys) = 1/2

(Number of girls)/20 = 1/2

Number of girls = 20/2

Number of girls = 10

 

Also,

Total number of students

= Number of girls + Number of boys

= 10 + 20

= 30 Students

 

∴ Total number of students in the class = 30

  1. Chapter 8 Class 8 Comparing Quantities
  2. Concept wise
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Davneet Singh
Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.