Free Study Material For RRB Examination
Subject : Mathematics (Alligation or Mixture)
It is the rule that is used to determine the mean value of
the mixture when the prices of the individual items being mixed together and the
proportion in which they are being mixed are given. Here, the value of the
mixture is always higher than the lowest value and lower than the higher value
of the items being mixed.
According to the Rule of Alligation
:. (Cheaper quantity : Dearer quantity) = (y – m) : (m – x)
Where, mean price (m) is the cost price of a unit quantity of
Also, if a container contains x units of liquid from which y
units are taken out and replaced by water.
Example 1: How many kilograms of rice costing ` 18 per
kg must be mixed with 30 kg of rice costing ` 14 per kg, so that the resultant
mixture cost ` 15 per kg.
Solution. Applying the rule of alligation, we have