(a) what is the probability that exactly two of the selected bulbs are rated 75-w
Answer: We are given:
Six 40-w lightbulbs,
Four 60-w bulbs,
Three 75-w bulbs
Now the probability of exactly two 75-w bulbs is:
P( two 75-w bulbs) = [tex] \frac{\binom{3}{2}\binom{10}{1}}{\binom{13}{3}} [/tex]
=[tex] \frac{3 \times 10}{286} [/tex]
=[tex] \frac{30}{286} =0.1049 [/tex]
Therefore, the probability that exactly two of the selected bulbs are rated 75-w is 0.1049
