Examples of Chain Rule 1

In this class, we discuss Examples of Chain Rule 1.

The reader should have prior knowledge of proportions and ratios. Click Here.

Directly Proportional: Two quantities are directly proportional. If the increase of one quantity then the other quantity increase to the same extent.

Example: Cost is directly proportional to the number of articles.

More articles cost more.

Indirectly Proportional: If one of the quantities increases, the other quantity decreases to the same extent.

Example: more speed, less time taken

Example 1:

If fifteen toys cost Rs 234, what do 35 toys cost?

Solution:

More toys more cost – Directly proportional

15: 35:: 234: x

Product of extremes = product of mean terms from proportions formulae

15 * x = 35 * 234

x = 546

Example 2:

If 36 men can do a piece of work in 25 hours, how many hours will fifteen men do it?

Solution:

Fewer men more hours – Indirectly proportional

Important to remember: We reverse the ratios for indirectly proportional

36: 15 written as 15: 36

15: 36:: 25: x

Product of extremes = product of mean terms

15x = 36* 25

x = 60

= 60 hours