### Chain Rule

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__Chain Rule__

Important Points :

**Rule of Three :**

The method of finding the 4th 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 :

i). More pens, more cost.

ii). 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 :

i). More speed, Less is the time taken.

ii). Less time to finish a work, more persons at work.