Ratio: Ratio is the comparison of two quantities by division. The ratio of a to b is written as
a: b= a/b= a+b
Proportion: A proportion is an expression which states that two ratios are equal.
Eg: 3/12=1/4 is a proportion
It can also be expressed as
3:12=1:4 or 3:12:: 1:4
Each quantity in proportion is called a term proportional. The first and last terms are called the extremes whereas the second and the third terms whereas the second and the third terms are called middle term.
Properties of Ratio:
1. In a ratio, two quantities are compared, so the quantities must be of the same kind.
2. The ratio of two quantities determines how many times of quantity is contained by the other.
Direct Proportion: If the price of pen rs.2 then the price of 5 pens will be rs.10.It so happens that as the number of pens increases the cost of the pens also increases in the same ratio.
Inverse Proportion: it would be easier to understand if by taking some example. Suppose 6 persons can do a piece of work in 15 days. To find the number of days taken to complete same piece of work when 10 persons are employed, we invert the proportions as follows:
6:10: x: 5
Mean Proportion: The mean proportional between two numbers is equal to the square root of their product.
