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SAI International School
Class VIII
Mathematics
Chapter 13- DIRECT & INVERSE PROPORTION
Lesson note
Subtopic: INVERSE PROPORTION INTRODUCTION & APPLICATION
INTRODUCTION INVERSE PROPORTION
Two quantities a and b are said to be in Inverse proportion if
a. Increase in a decreases the b
b. Decrease in a increases the b
In such a case if b1, b2 are the values of b corresponding to the values a1, a2 of a
respectively then,
a1b1 = a2b2 = k,
When two quantities a and b are in inverse proportion then they are written as a ∝ 1/b
This shows that as the distance of the figure from light increases then the brightness to
the figure decreases.
Example
If 15 artists can make a statue in 48 hours then how many artists will be required to do
the same work in 30 hours?
Solution:
Let the number of artists required to make a statue in 30 hours be y.
Number of hours 48 30
Number of artists 15 y
