Class 6 Chapter 12 Ratio and Proportion Math Formulas

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A ratio is a mathematical expression of comparing two quantities by division.

It is written using ‘:’


For Example:- 5: 2.


Note: – The unit must be same to compare two quantities


Equivalent Ratios:-

If we multiply or divide both the numerator and denominator to the same number then we find the equivalent ratio.


For example:- \frac{1}{2}, \frac{2}{4}, \frac{4}{8}


The Lowest form of the Ratio:-

If there is no common factor of numerator and denominator except one then it is the lowest form of the ratio.

For eg –  \frac{1}{2} , \frac{3}{5}, etc.



When we say that two ratios are equal then it is called Proportion.

\frac{a}{b} = \frac{c}{d}

It is written as a:b::b:c
Unitary Method:-

If we find the value of one unit then calculate the value of the required number of units this  is called the Unitary method.


For example:-

If the cost of 4 books is 320 Rs. then what will be the cost of 8 books?

Cost of 3 books = Rs. 320

Cost of 1 book = \frac{320}{4} = Rs. 80

Cost of 6 books =  \frac{320}{4} \times 8 = Rs. 640