Ratio is just a way to compare two quantities while the proportion is an equation which shows that two ratios are equivalent. The concept of ratio and proportion is one of the most essential concepts in maths. This introduction to these concepts covers all the related concepts with solved examples.
Ratios
In certain circumstances, the comparison by the process of division makes good sense when compared to performing their difference. Hence, the comparison of two quantities by the process of division method is called as ‘Ratio’ between two numbers.
The two numbers in a ratio can only be compared when they have the same unit. We make use of ratios to compare two things. The sign used to denote a ratio is ‘:‘.
A ratio can be written as a fraction, say 2/5. Or can write it by using “to”, as “2 to 5.”We happen to see various comparisons or say ratios in our daily life.
Proportion
Ratio and proportions are said to be faces of the same coin. When two ratios are equal in value, then they are said to be in proportion. In simple words, it compares two ratios. Proportions are denoted by the symbol ‘::’ or ‘=’.
Ratio and Proportion Formula
Suppose we have two quantities or two numbers or two entities and we have to find the ratio of these two, then the formula for ratio is defined as;
a : b ⇒ a/b
where, a and b could be any two quantities. You can also learn ratio formula completely here.
Now, let us assume that, in proportion, the two ratios are a:b & c:d. The two terms ‘b’ and ‘c’ are called ‘means or mean term,’ whereas the terms ‘a’ and ‘d’ are known as ‘extremes or extreme terms.’
a/b = c/d or a : b :: c : d 
Let us consider one more example of a number of students in a classroom. Our first ratio of the number of girls to boys is 3:5 and that of the other is 4:8, then the proportion can be written as
3 : 5 :: 4 : 8 or 3/5 = 4/8
Here 3 & 8 are the extremes, while 5 & 4 are the means.
Continued Proportion
Consider two ratios to be a:b and c:d.
Then in order to find the continued proportion for the two given ratio terms, we convert the means to a single term/number. This would, in general, be the LCM of means.
For the given ratio, the LCM of b & c will be bc.
Thus, multiplying the first ratio by c and second ratio by b, we have
First ratio ca:bc
Second ratio bc: bd
Thus, the continued proportion can be written in the form of ca:bc:bd
Ratio and Proportion Tricks With Example Questions
Question 1: Are the ratios 4:5 and 8:10 said to be in Proportion?
Solution:
4:5= 4/5 = 0.8 and 8: 10= 8/10= 0.8
Since both the ratios are equal, they are said to be in proportion.
Question 2: Are the two ratios 8:10 and 7:10 in proportion?
Solution:
8:10= 8/10= 0.8 and 7:10= 7/10= 0.7
Since both the ratios are not equal, they are not in proportion.
Question 3: Given ratio are
a:b = 2:3
b:c = 5:2
c:d = 1:4
Find a:b:c.
Solution: Multiplying the first ratio by 5, second by 3 and third by 6, we have
a:b = 10: 15
b:c = 15 : 6
c:d = 6 : 24
In the ratio’s above, all the mean terms are equal, thus
a:b:c:d = 10:15:6:24
Question 4: Out of the total students in a class, if the number of boys are 5 and the number of girls being 3, then find the ratio between girls and boys.
Solution: The ratio between girls and boys can be written as 3:5( Girls: Boys). The ratio can also be written in the form of factor like 3/5.
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