What is the IQ of a student whose physical (chronological) age and mental age are the same?

Correct answer: 100. IQ = (mental age ÷ chronological age) × 100, so equal ages give an IQ of 100.

• 90: 90 would mean mental age is below chronological age.
• 110: 110 would mean mental age is above chronological age.
• 120: 120 would mean mental age is well above chronological age.