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Introduction to Direct and Inverse Proportions
There are so many situations in our life where we see some direct or indirect
relationship between two things. Like

 If the number of things purchased is increasing then the amount to pay will
also increase.

 If the speeds of the car will increase then the time to reach the destination
will decreases.

Variations
If the value of two objects depends upon each other in such a way that the increase
or decrease in the value of one object affects the value of another object then these
two objects are said to be in variation.
Direct Proportion
Two quantities a and b are said to be in direct proportion if

 Increase in a increases the b

 Decrease in a decreases the b
But the ratio of their respective values must be the same.

 a and b will be in direct proportion if a/b = k(k is constant) or a = kb.
 In such a case if b1, b2 are the values of b corresponding to the values a1,
a2 of a respectively then, a1/b2 = a2/b1 ​

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