Probability that workers on strike = P (S) = 0.65 Probability that job was completed on time =P(W)=0.8 Probability that the job was completed when the workers were on strike P(Ws)=0.32 ∴ Required probability =P(W)P(S)+P(S)P(Ws) =0.8×0.35+0.65×0.32 =0.488