What is the formula used to calculate IQ?

The formula used to calculate IQ, or Intelligence Quotient, is based on the concept of mental age and chronological age. Specifically, the correct formula is the mental age divided by chronological age, and then that result is multiplied by 100 to eliminate decimals and to create a standardized score. This approach allows for the comparison of an individual's cognitive abilities with those of their peers.

The multiplication by 100 is crucial as it sets the average IQ score at 100, making it easier to interpret. A score above 100 indicates cognitive abilities above the average for the individual's age group, while a score below 100 suggests below-average abilities.

In this context, the other choices do not accurately represent the conventional method of calculating IQ. For instance, simply dividing mental age by actual age without multiplying by 100 would not yield a standardized IQ score. Multiplying mental age by actual age or subtracting mental age from actual age does not relate to established formulas and would not produce a meaningful measure of intelligence in the context of IQ assessments.