Aptitude - Chain Rule

Rule of Three

The method of finding the 4^th proportional when the other three are given is called Simple Proportion or Rule of Three

Compound Proportion

Repeated use of Rule of Three is called compound proportion.

Direct Proportion

Two quantities are said to vary directly, if on the increase (or decrease) of the one, the other increases (or decreases) to the same extent.

Examples :
More pens, more cost.
More men, more work.

Indirect Proportion

Two quantities are said to vary indirectly, if on the increase (or decrease) of the one, the orther decreases (or increases) to the same extent.

Examples :
More speed, Less is the time taken.
Less time to finish a work, more persons at work.