Answer:

Step-by-step explanation:
<u>Conditional Probability</u>
Is a measure of the probability of the occurrence of an event, given that another event has already occurred. If event B has occurred, then the probability that event A occurs is given by:

Where
is the probability that both events occur and P(B) is the probability that B occurs.
Let's define events A and B for the question. There are 11 students that have a brother and 9 that have a sister. Two of those students have a brother and a sister.
We are given the fact that the selected student has a brother: this is the event that has already occurred, thus:
B = A student has a brother
A = A student has a sister
The probability that a student has a brother is:

The probability that the student has a brother and a sister is:

Thus, the conditional probability is:

Simplifying:

Given:
unit price per pound = 21.5 cents
bought 8 pound package
find: total amount paid for 8 pound package.
We need to convert cents into dollars to avoid confusion.
21.5 cents x 1 dollar / 100 cents = 21.5 dollar / 100 = 0.215 dollars
0.215 dollars * 8 pounds = 1.72 dollars.
my answer is B. $1.72
The answer is : Both plane A and B.
Their average is <em>59/144 .</em>