00:01
All right, so we're given that in particular fleet indicates 70 % in the plane expect to have no wing cracks, 25 have a detectable, and five have critical wing cracks.
00:11
So we sample five of them, or five are individually selected, so we want to find the probability that one has a crack.
00:18
It's a probability that one has a crack.
00:28
So that'll be a probability of five choose one times.
00:41
Oh, one has a critical crack.
00:46
So that would be 0 .05 to power 1 times 0 .95 to the power 4.
00:57
So we can toss that into the calculator.
01:00
5 choose 1 times 0 .05 times 0 .95 to the power of 4.
01:12
And that would be about 20%.
01:15
Then we want to know that two have the technical cracks.
01:20
Probability of two so that will be five choose two so the detectable crack is 25 % so 0 .252 times 0 .75 to the third and that will give us 0 .26 and the last one of that says and two have no cracks so five choose two so having no cracks, 70 % squared times 0 .03.
02:22
I'm sorry, 0 .3 to 3.
02:41
And that will be 0 .13.
02:48
For b, he says find the probability that at least one has a critical crack.
02:58
So at least one, so that would be, so we can rewrite this as just one minus the probability of none having a crack...