If the prevalence of blindness in a population is 0.005, and prevalence of deafness is 0.001, the total prevalence of deafness and blindness together is:

By the law of multiplication of probability, when two events are not mutually exclusive, the total probability is obtained by multiplying the individual probabilities. P(deafness and blindness)= P(deafness)x P(blindness)= 0.005x0.001=0.000005 Ref: Medical biostatistics, 1st edition pg: 191