Ratio and Proportion -> IMPORTANT FACTS AND FORMULAE
Ratio : The ratio of two quantities a and b in the same units, is the fraction a/b and we write it as a : b. | |
Proportion : The equality of two ratios is called proportion. | |
Mean Proportional : Mean Proportional between a and b is √ab. | |
Fourth Proportional : If a : b = c : d, then d is called the fourth proportional to a,b,c. | |
Third Proportional : If a : b = b : c, then c is called the third proportional to a and b. | |
Duplicate ratio : of (a : b) is (a^{2} : b^{2}). | |
Sub-duplicate ratio : of (a : b) is (√a : √b). | |
Triplicate ratio : of (a : b) is (a^{3} : b^{3}). | |
Variation : (I). We say that x is directly proportional to y, if x = ky for some constant k and we write, x∝y. (II). We say that x is inversely proportional to y, if xy = k for some constant k and we write, x∝1/y. |