Inverse Proportion

Direct Proportion

Inverse Proportion

Before you study what is inverse proportion, you are advised to read: What are Ratio's ? What is Proportion ? Under Inverse Proportion, two quantities change in such a manner that if one quantity increases, other quantity decreases and vice-versa Or we can say that, two quantities x and y varies in inverse proportion when increase in x causes a decrease in y (and vice versa) in such a way that the product of their corresponding values remains constant (i.e. k) That is if: xy = k Then x and y are in inverse proportion And when y1 & y2 values of y correspond to values x1 & x2 of x, then we get: x1/x2 = y2/y1 Or we can also write it as: x1 y1 = x2 y2 When two quantities, x & y are in inverse proportion or vary inversely, we write it as x ∝ 1/y Example 1: Observe the following table: Quantity 'x' 10 20 30 Quantity 'y' 6 3 2 In the above table you can observe that: When quantity of x increases from 10 to 20, the quantity of y decreases from 6 to 3 Again, when quantity of x increases from 20 to 30, the quantity of y decreases from 3 to 2 This shows that there is an inverse relation between quantity x and y. Also, you can observe that: x1 y1 = x2 y2 10 X 6 = 20 X 3 (Because on solving LHS and RHS we get 60 on both sides) Similarly; X2 y2 = x3 y3 20 X 3 = 30 x 2 (Because on solving LHS and RHS we get 60 on both sides) Since we get xy = K ( k being 60 in all cases), We can say that quantity x and quantity y varies in inverse proportion.