What Is meant by Proportion ?

Proportion:

• A proportion is simply a statement that two ratios are equal.
• It can be written in two ways: as two equal fractions $\frac{a}{b}$ = $\frac{c}{d}$; or using a colon, a:b = c:d. 'a' and 'd' are known as extremes and 'b' and 'c' are known as means
• For example,  3:2 = 6:4
• Proportion Rule: Product of extremes = Product of means. 

          If $\frac{a}{b}$ = $\frac{c}{d}$ means we get ad = bc