Definition of rule of three in English:

rule of three

Syllabification: rule of three

noun

Mathematics , dated
A method of finding a number in the same ratio to a given number as exists between two other given numbers.
More example sentences
  • The mathematics involves a study of proportion and percentages and introduces the rule of three for solving proportion problems.
  • If the fruit diminish as the requisition increases, or augment as that decreases, they, who are skilled in accounts, consider the rule of three to be inverted.
  • The rule of three is the familiar way of solving problems of this type: if a man earns 50 dinaras in 8 days how much will he earn in 12 days?