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SAI International School
Class VIII

Mathematics
Chapter 13– Direct & Inverse Proportion
Lesson notes
Subtopic: Direct Proportion Introduction & Application

SUBTOPICS:
Recap of ratio and proportion
INTRODUCTION DIRECT PROPORTION

We have already discussed ratio and proportion in class 7.Lets see few example
before starting DIRECT AND INVERSE PROPORTION .

Ratio and Proportion Examples

Question 1: Are the ratios 4:5 and 8:10 said to be in Proportion?
Solution:

4:5= 4/5 = 0.8 and 8: 10= 8/10= 0.8

Since both the ratios are equal, they are said to be in proportion.

Question 2: Are the two ratios 8:10 and 7:10 in proportion?
Solution:

8:10= 8/10= 0.8 and 7:10= 7/10= 0.7
Since both the ratios are not equal, they are not in proportion.

Ratio and Proportion Word Problems

Question 4: Out of the total students in a class, if the number of boys is 5 and
the number of girls being 3, then find the ratio between girls and boys.

Solution: The ratio between girls and boys can be written as 3:5 ( Girls: Boys). The
ratio can also be written in the form of factor like 3/5.

Question 5: Two numbers are in the ratio 2 : 3. If the sum of numbers is 60,
find the numbers.

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