The formula for Educational Quotient is -

Concept: In psychometrics, a “quotient” expresses a specific attainment measured in “age” units as a percentage of Chronological Age (CA), following the general pattern Quotient = (Relevant Age / Chronological Age) × 100. The Intelligence Quotient (IQ) plugs in Mental Age (MA) as the relevant age; the Educational Quotient (EQ) plugs in Educational Age (EA) — the age level a student's scholastic/academic performance corresponds to.

Application: Substituting Educational Age for the relevant-age term gives EQ = Educational Age / Chronological Age × 100 — exactly the ratio Educational Age / Chronological Age × 100.

Cross-check by contrast — why the other ratios do not define EQ:

• Mental Age / Chronological Age × 100 is the Intelligence Quotient formula — it measures general mental ability, not scholastic attainment, so it defines IQ, not EQ.

• Mental Age / Educational Age × 100 divides one age measure by another without ever bringing in Chronological Age, so it does not follow the quotient pattern used to define any standard psychometric measure.

• Chronological Age / Mental Age × 100 inverts the numerator and denominator of the Intelligence Quotient ratio — a quotient built this way would fall as ability rises, which is the opposite of how quotient measures are meant to behave.

Result: only Educational Age / Chronological Age × 100 follows the standard quotient pattern for scholastic attainment, so it is the formula for the Educational Quotient.