Types of Proportion:
In other words, If increase in one quantity causes increase in other quantity or decrease in one quantity causes decrease in other quantity, then we say that they are related directly (They are direct proportion).
If and are in direct proportion, then division of and will be constant.
In the above example, we see that
each ratio is the same.
Hence, if we are dealing with quantities, which are related directly, (which are in direct proportion), then we shall use the follow rule.
24 x 240 = 12 x 480
Principle of Direct Proportion
If 30 dozens of eggs cost 300 Rs. Find the cost of 5-dozens of eggs.
Let be the required price of 5 dozens eggs
Since quantities are in direct proportion, so we use the above principle.
x 30 = 5 x 300
= 50 Rs. Example:
A car travel 81 km in 4.5 liters. How far will it goes by 20 liters of petrol.
Let be required required distance travelled by car in 20 liters.
Since quantities are related directly, so by the above principle
4.5 x = 20 x 81
= 360 km