The prevalence of dental caries in a community in the year 2000 and 2003 was 18% and 38% respectively. The incidence of caries for the same population in three years would be:
Hint:
Incidence  = No. of new cases in a specified time (38-18 = 20%)
Prevalence = Incidence x Duration.  
Incidence = Prevalence / Duration = P/D.
38%
20%
10%
56%