The equality of two ratios is called proportion.In other words,
If two ratios are equal then the two ratios or the quality of two ratios make a proportion.
Since 2:5 = 4:10 and say that 2,5,4,10 are in proportion.
properties of proportion
- If the proportion is a:b::c:d , then the quantities a and b must be of the same kind, c and d may be of the same kind or of different kind.
- The quantities of proportion are called sequentially as 1st,2nd 3rd,4th term.
The multiplication of 1st and 4th term will be equal to the multiplication of 2nd and 3rd term.
let 2:3 = 10:15 as a proportion.
so, 1st term=2, 2nd term=3, 3rd term=10, 4th term=15.
let 3:5 = 9:15 as a proportion.
Here, 1st term=3, 2nd term =5, 3rd term =9, 4th term =15
so, 1st x 4th = 3 x 15 = 45
2nd x 3rd = 5 x 9 = 45
So, it can be say that if a:b = c:d, then ad = bc
Note: Proportion can be restated as "two sets of numbers are in proportion to one another when one set is a constant times the other"
If the price of 3kg and 6kg rice is 6 dollar and 12 dollar respectively.Then
|3:6 = 6:12||or||3||=||6|
So, here we can see the Consequent of the 1st ratio is equal to the Antecedent of the 2nd ratio.
Now we can say that 3,6,12 are in Continued proportion.