Definition
A mathematical statement that two ratios are equal, expressed in the form a:b = c:d or a/b = c/d. Used in maintenance calculations to find an unknown value when three of the four related quantities are known.
Plain English
Two pairs of numbers that share the same relationship. If you know three of the numbers, you can work out the fourth.
Context Anchor
Seen in maintenance math when scaling drawings, converting measurements, or calculating mixture amounts.
Derivation
From Latin proportio, meaning 'comparative relation.' It describes how one quantity relates to another in size or amount.
Why Pilots Care
Technicians use proportions for fuel/oil mixing, scaling drawings, calculating gear ratios, and converting measurements. Getting the proportion wrong means getting the answer wrong.
Analogy
A recipe is a simple proportion. If 2 cups of mix make one batch, then 4 cups make two batches because the relationship stays the same.
Intuition Check
Proportion does not just mean a rough amount here. In this math use, it means two ratios are equal.
Example Sentence 1
The technician used a proportion to find the correct oil quantity for the fuel mixture.
Example Sentence 2
Mixing the composite required maintaining the correct proportion of resin to hardener.