The document discusses direct and inverse proportions. It provides examples of direct proportions involving cost of eggs based on dozens, distance traveled by a car based on fuel used, and examples of inverse proportions involving time to fill a tank based on number of pipes and days to build a house based on number of workers. Direct proportion means that as one quantity increases, the other also increases or as one decreases, the other decreases. Inverse proportion means that as one quantity increases, the other decreases or vice versa. The examples show setting up proportions to solve for unknown values related to the quantities that are directly or inversely proportional.

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2. BY: ASSOCIATE PROFESSOR NADEEM UDDIN
Direct Proportion:
If two quantities are in direct proportion as one increases, the other increases or
one decreases the other decreases.
Example-14
If 30 dozens of eggs cost Rs.300.Find the cost of 5 dozens eggs.
Solution:
Cost Dozens
300 30
x 5
x 5
=
300 30
5
x = 300
30
x = Rs.50

Example-15
A car travel 81 km in 4.5 liters. How far will it goes by 20 liters of petrol.
Solution:
Km Liters
81 4.5
x 20
x 20
=
81 4.5
20
x =
4.5
x = 360 km
 

3. Inverse Proportion:
If increased in one quantity causes decreased in other quantity or decrease in one
quantity,causes increased in other quantity then we say that both quantities are
inversely related.
Example-16
Four pipes can fill a tank in 70 minutes. How long will it take to fill the tank by 7
pipes?
Solution:
Minutes Pipes
70 4
x 7
x 4
=
70 7
4
x =
7
x = 40 minutes
 
Example-17
35 workers can build a house in 16 days. How many days will 28 workers working
at the same rate take to build the same house?
Solution:
Days workers
16 35
x 28
x 35
16 28
35
x 16
28
x 20 days
=
= 
=