00:01
Three car brands, a, b, and c, all have the market share in a certain city.
00:05
Brand a has 20%, brand b has 30%, and brand c has 50 % of the market share.
00:16
The probability that a brand a car needs a major repair during the first year of purchase is 0 .05.
00:25
The probability that brand b needs a repair, and the first year of purchase is 0 .10, and the probability that c needs a repair in the first year is 0 .15.
00:38
What is the probability that a randomly selected car in the city needs a major repair during its first year of purchase? so i'm just going to put that as probability of repair.
00:47
And that's going to be multiplying each of these branches and then adding up those numbers.
00:54
So 0 .2 times 0 .05 is 0 .01.
00:58
Then we'll add 0 .3 times 0 .10, which is 0 .01 .1 .3 times 0 .10, which is 0.
01:02
0 .03 and 0 .5 times 0 .15, which is 0 .075, for a total probability of 0 .115.
01:12
Next, we're going to find the probability.
01:15
If a car in the city needs a major repair during its first year purchase, what's the probability that it is a brand a car? so that would be the probability that it is car a, given that it needs repairs.
01:30
So first we're going to find the probability of a and r, which is 0 .2 times 0 .05, which is equal to 0 .01.
01:38
And then we're going to divide it by the probability of r, which we already found to be 0 .115...