rule of three

noun Mathematics.

the method of finding the fourth term in a proportion when three terms are given.

Words nearby rule of three

rule of eleven, rule of engagement, rule of law, rule of outlet, rule of the road, rule of three, rule of thumb, rule out, rule the roost, ruled surface, ruleless

Origin of rule of three

First recorded in 1585–95

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

Examples from the Web for rule of three

I do not require to examine on this point, as I consider it to be a rule-of-three calculation.
Diary in America, Series Two|Frederick Marryat (AKA Captain Marryat)
Boys were never taught the rule-of-three until after they had learnt addition.
Essays on Education and Kindred Subjects|Herbert Spencer
When it was found that he could not do decimals, he was put back to the rule-of-three, and then pronounced incurable.
Homes and haunts of the most eminent British poets, Vol. II (of 2)|William Howitt
It is as if we were to talk of the color of sound, or the longitude of the Rule-of-three.
Prose Masterpieces from Modern Essayists|James Anthony Froude, Edward A. Freeman, William Ewart Gladstone, John Henry Newman and Leslie Stephen

A man who's seen Injin fightin' don't go much on this here West Point fightin' by rule-of-three—but that ain't here or there!
Clarence|Bret Harte

British Dictionary definitions for rule of three

rule of three

noun

a mathematical rule asserting that the value of one unknown quantity in a proportion is found by multiplying the denominator of each ratio by the numerator of the other

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012