00:01
Okay, we have here then a binomial type problem where p of not on time is 0 .05, which means p of on time is 1 minus that, so 0 .95.
00:20
So late then, 0 .05, on time, 0 .95.
00:26
The first one, what they want is p of all three on time.
00:32
P of three on time.
00:38
Well on time is 0 .95, the three of them cubed.
00:44
0 .95 times 0 .95 times 0 .95 times 0 .95.
00:49
And that will be 0 .857, 375, but that should be enough places.
01:03
Three places should be okay.
01:06
So 857 for that one.
01:09
Part b is exactly 1 is not on time.
01:16
So p of 1 late will say.
01:22
Well, late is 0 .05, not on time.
01:28
Other two are fine, so 0 .95 squared.
01:33
And this one that's late could be first, second or third, so you times that by three.
01:39
Or three ways to have one being late.
01:44
First late, second one late, third one.
01:46
One late.
01:47
That i work out.
01:49
0 .05 times 0 .95 squared times three...