Answer:a) Probability P(exactly 2 bulbs rated 13watts)= 0.22
b) Probability(each bulb different rating)
= 0.24
Step-by-step explanation:
There are 6 13watts bulbs
8 18watts bulbs
4 23watts bulbs
Total bulbs = 18
a) Probability that all 3 bulbs are 18watts
Number of ways of pulling 3 bulbs = 18!/(3!×15!) = (6.4×10^15)/7.846×10^12) = 815 ways
Different ways of pulling 13watts bulbs out of 6 = 6!/(2!×4!)= 720/48=15ways
Different ways of pulling non 13 watts bulbs= 12!/(1!×11!) = 479,001,600/ 39,916,800 = 12
Number of ways total= 15×12=180waya
Therefore P(exactly 2 bulbs rated 13watts)= 180/815 =0.22
b) Probability P( all 3 bulbs are 1 from each rating)
Ways of pulling 3bulbs bulb each from 3 ratings are 4× 5 × 8= 192ways
Probability = 192/815 =0.24
