In a single word the mean of VARIATION is change. If we say about Variation, that means a change in one quantity in relation to the change in another. In the examples we have considered so far, one quantity (cost or weight) increases or decreases correspondingly with the other quantity (the number of things), here we say that one quantity varies directly as the other quantity. But this is not always the case, here one quantity (number of days) decreases when the other quantity (the number) increases, we can say that one quantity varies inversely as the other quantity.
So, variation can be of two types 1) Direct and 2) Inverse.
Direct Variation –
Two quantity ‘A’ & ‘B’ are said to vary directly or be in direct variation or in direct proportion if the change in such a way that the ratio of two values of ‘A’ is the same as the ratio of the corresponding two values of ‘B’. Here the cost of any product directly varies with the cost of the particular product.
Inverse Variations –
If two quantity ‘A’ & ‘B’ are said to vary indirectly or be in inverse variation or in inverse proportion, if they change in such a way that the ratio of two values of ‘A’ is the same as the inverse ratio of the corresponding two values of ‘B’. In a simple way to better understand we can say that, number of workers inversely or proportionately varies, if the number of workers increases then given work can be finished a very short period of time but if the number of workers reduces then to complete the same job more days are needed.