Answer: 0.99483
Step-by-step explanation:
Given : A box contains four 40-W bulbs, five 60-W bulbs, and six 75-W bulbs.
Total bulbs : 4+5+6=15
The probability of selecting a 75-W bulb :
Using the binomial probability :-
, where P(x) is the probability of getting success in x trials , p is the probability of getting success in each trial and n is the total number of trials.
We have,
The probability that at least two bulbs must be selected to obtain one that is rated 75W :-
Hence, the required probability = 0.99483