A box in a certain supply room contains four 40-W lightbulbs, five 60-W bulbs, and six 75-W bulbs. Suppose that three bulbs are randomly selected. What is the probability that exactly three of the selected bulbs are rated 75-W? (15 points)

Probability that exactly three of the selected bulbs are rated 75-W is 0.044.

Step-by-step explanation:

We are given that a box in a certain supply room contains four 40-W light bulbs, five 60-W bulbs, and six 75-W bulbs.

And we have to find the probability that exactly three of the selected bulbs are rated 75-W.

Here, we will use Combinations for selection procedure, i.e.;

So, number of ways of selecting three 75-W rated bulbs from total of six 75-W rated bulbs in a box is given by =

Total number of ways of selecting three bulbs from total of 15 bulbs (4 + 5 + 6) in a box =

Therefore, probability that exactly three of the selected bulbs are rated 75-W is given as = =

                             = = =

                             = 0.044

Hence, the required probability is 0.044.