“The proportion involving two or more quantities is called Compound Proportion” Rules for Solving Compound Proportions
CASE-1
If quantity 1 and quantity 2 are directly related and quantity 2 and quantity 3 are also directly related.
Then we use the following rule
CASE-2
If quantity 1 and quantity 2 are directly related and quantity 2 and quantity 3 are inversely related.
Then we use the following rule
CASE-3
If quantity 1 and quantity 2 are inversely related and quantity 2 and quantity 3 are directly related.
The we use the following rule
CASE-4
If quantity 1 and quantity 2 are inversely related and quantity 2 and quantity 3 are also inversely related.
Then we use the following rule
Example:
195 men working 10 hour a day can finish a job in 20 days. How many men employed to finish the job in 15 days if they work 13 hours a day.
Solution:
Let  be the no. of men required
20 x 10 x 195 = 15 x 13 x 
 = 200 men
Example:
A soap factory makes 100 units in 9 days with help of 20 machines. How many units can be made in 12 days with the help of 18 machines?
Solution:
20 x 9 x  = 600 x 18 x 12
 = 720 units
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