This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Social & Preventive Medicine
Prevalence is calculated by formula(2018) 
Select and explain. 
A. Incidence x Mean durationx100, B. Incidence/ Mean duration x 100, C. Incidence/Mean duration, D. Incidence x Mean duration
D: Incidence x Mean duration
Answer: D: Incidence x Mean duration 
Explanation: Relationship between prevalence and incidence Prevalence depends upon 2 factors, the incidence and duration of illness. Given the assumption that the population is stable, and incidence and duration are unchanging, the relationship between incidence and prevalence can be expressed as : P= IxD = incidence x mean duration Ref:- park; pg num:- 69