**Important Concepts and Formulas on Ratio and Proportion**

2. While calculating the ratio of two
given quantities, both the quantities must be in the same unit.

3. The ratio a : b is not same as the
ratio b : a.

4. The first term of a ratio is called
the antecedent and the second term is called the consequent.

5. Normally a ratio is expressed in its
simplest form.

7. We can compare two ratios by converting
the ratios in their fractional forms.

8. If two ratios are equivalent, then
the four quantities involved in these two ratios are said to be in proportion. Four
quantities a, b, c, d are said to be in proportion if a : b = c : d.

9. First and fourth terms (i.e., end
terms such as a and d) of a proportion are called extremes and the middle terms
(i.e., the second and third terms such as b and c) are called means.

10. If four terms are in proportion, then
product of extremes = product of means.

11. The rule ad = bc is used to check
whether a, b, c, d are in proportion or not.

12. A method in which we first find the
value of one unit and then find the value of the required number of units is
called unitary method.