00:01
We're given their 20 apartments and the probability of an apartment that will not be rented is 0 .1.
00:06
And if the landlord can rent out a minimum of 16 apartments, he can meet all his money expenses.
00:14
Now we want to figure out which probability is more useful to the landlord to meet his expenses.
00:21
Exactly four unrented units probability or the probability of four or fewer unrented units.
00:28
I'm going to let x be the number of un rented apartment out of this 20 apartment.
00:42
So we know that the x will follow a binomial distribution and is 20.
00:48
Probability of an apartment not rented out is 0 .1.
00:53
So probability of x equals to r is 20 choose r, 0 .1 to power of r, and 1 minus 0 .1 and 0 .9 to the power of 20 minus r.
01:06
So we were to look at probability of exactly four unrented units.
01:12
That will be probability x equals to 4.
01:15
So i'm just going to sub in 4 into the r here.
01:25
And we will get 0 .088 for decimal place.
01:33
Now for probability, four or fewer unrented units will be x...