This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Social Science, Mental Health & Genetics, Subject name: Social & Preventive Medicine
IQ is calculated by - 
Select and explain. 
A. Mental age/chronological age, B. Mental age - chronological age, C. Chronological age/mental age, D. Chronological age - mental age
A: Mental age/chronological age
Answer: A: Mental age/chronological age 
Explanation: Ans. is 'a' i.e., Mental age/Chronological age The Intelligence Quotient (I.Q.) is calculated according to the formula:The WHO classification of mental retardation is based on the concept of IQ and includes the following categories:CategoryIQMild50-70Moderate35-49Severe20-34Profound<20A child with IQ <70 is called mentally retarded.