00:01
In its question, we're given from experience, the landlord knows probability an apartment and complex will not be rented is 0 .1, and there are 20 apartments in the complex.
00:13
The rental status for each apartment is independent of the others, and the landlord can meet all monthly expenses if there's a minimum of 16 apartments they are rented.
00:22
I'm going to let x be the number of units of 20 that are unrented.
00:26
So n, the number of trials will be 20 since there are 20 apartments here.
00:33
And in this trial, we take a look at whether the apartment can be rented or not.
00:41
So all the 20 trials are identical.
00:44
And we have p, probability of success in a single trial.
00:47
There's probability a complex will not be rented.
00:51
It's 0 .1.
00:52
And this remains constant because this comes from a statistics.
00:56
So that's constant.
00:59
So x will follow the binomial distribution, n is 20, p is 0 .1.
01:05
The probability of x equals to r, where r is the number of units are of 20 that is unrented.
01:10
That will be 20 choose r, 0 .1 to power r, and 1 minus 0 .1, 0 .9 to the power of 20 minus r.
01:21
In part a, want to find probability...