2 varying quantities are said to be in a relation of proportionality if they are multiplicatively connected to a constant

The value of this constant is called the coefficient of proportionality or proportionality constant

The relation is often denoted using the symbols ”∝” or ”~”:

  • 𝑦 ∝ 𝑥
  • 𝑦 ~ 𝑥

Proportion - Types

Direct Proportion

Inverse Proportion

𝑦 is directly proportional to 𝑥 if there is a non-zero constant 𝑘 such that:

  • 𝑦 = 𝑘𝑥

𝑦 is inversely proportional to 𝑥 if there is a non-zero constant 𝑘 such that:

  • 𝑦 = 𝑘/𝑥
  • 𝑥𝑦 = 𝑘