Problem description:
Only two factories produce lamps of a certain type.
Among the products of the first factory, 2% lamps are defective lamps, among the products of the second - 3%.
It is known that with a randomly selected lamp, the probability of buying a bad lamp of this type is 0.024.
Find the probability that a randomly selected lamp was produced in the first factory.
Problem solution:
Let P be the probability that the lamp was made by the first factory.
Then the probability that the lamp is made in the second factory is 1- P.
The probability the lamp is made in the first factory and at the same time is defective equals to 0.02 × P.
Similarly, the probability that the lamp is made in the second factory and at the same time is bad is 0.03 × (1- P).
Since the probability of buying a faulty lamp is 0.024, according to the formula for adding probabilities, we get the equation:
0.02 × P + 0.03 × (1 - P) = 0.024
Solving this linear equation, we could find: P = 0.6
Answer: the probability a randomly selected lamp is from the first factory is 0.6.
Next probability problem solution:
Calculate probability coffee remains in both machines, by the end of the day.
