The probability that a washing machine will operate satisfactorily for 3 years is 0.82 while the probability that a floor polisher will operate satisfactorily over the same period of time is 0.78. Find the probability that in a 3-year period, only the floor polisher will operate satisfactorily.
I already got, P(A and B) = 0.78(0.82) = 0.6396
I'm not sure if I should subtract it with 0.78 or 0.82
To find the probability that only the floor polisher will operate satisfactorily in a 3-year period, you need to subtract the probability that both the washing machine and the floor polisher will operate satisfactorily from the probability that only the floor polisher will operate satisfactorily.
The probability that both the washing machine and the floor polisher will operate satisfactorily is given by P(A and B) = 0.78(0.82) = 0.6396.
To find the probability that only the floor polisher will operate satisfactorily, you need to subtract this probability from the probability that the floor polisher will operate satisfactorily, which is given as 0.78.
P(only floor polisher operating satisfactorily) = P(floor polisher operating satisfactorily) - P(both operating satisfactorily)
P(only floor polisher operating satisfactorily) = 0.78 - 0.6396 = 0.1404.
So, the probability that only the floor polisher will operate satisfactorily in a 3-year period is 0.1404.