Study Materials for IBPS, Bank Exams : Numerical Ability/Quantitative Aptitude - Unitary Method

Direct Proportion

Two quantities are said to be directly proportional, if on the increase in one the other increases proportionally or on the decrease in one the other decreases proportionally.
eg, More the numbers of articles, more is the cost.
More the number of workers, more is the work done.
Less the number of articles, less is the cost.
Less the number of workers, less is the work done.

Indirect Proportion

Two quantities are said to be indirectly proportional, if on the increase in one the other decreases proportionally or on the decrease in one the other increases proportionally.
eg, More the number of workers, less is the number of days required to finish a work. More the speed, less is the time taken to cover a certain distance.
Less the number of workers, more is the number of days required to finish a work. Less the speed, more is the time taken to cover a certain distance.

Chain Rule

When a series of variables are connected with one another, that we know how much of the first kind is equivalent to a given quantity of second, how much of the second is equivalent to a given quantity of the third and so on. The rule by which we can find how much of the last kind is equivalent to a given quantity of the first kind is called the Chain Rule.