It was reported that the performance of candidates in this question was not commendable.  They found it difficult; hence they scored very low marks.  They were expected to show that if P(M) = probability of the malaria patient surviving = 0.27, probability of not surviving, P(M¢) = 1- 0.27 = 0.73.  Similarly, if P(T) = probability of the thypoid patient surviving = 0.85, then probability of not surviving = P(T1)  =  1-P(T) = 1- 0.85 = 0.15.  Probability of either surviving = (0.27 x 0.15) + (0.85 x 0.73) = 0.66. Probability of neither surviving =

(0.73 x 0.15) = 0.11.  Probability of at least one surviving = 1- 0.11 = 0.89.