Mathematics for IGCSE & O level - Probability (Section 8 - No. 28)
If the probability that Salima walks to school is 0.5, cycles is 0.2, and she goes by bus is 0.3. If she walks, the probability she's on time is 0.2. If she cycles, it's 0.1. If she goes by bus, it is 0.4. What is the probability that, on any given day, she is on time for school?
0.10
0.27
0.02
0.32
Paliwanag
0.5*0.2 + 0.2*0.1 + 0.3*0.4= 0.10+0.02+0.12 = 0.24