In a class of 28 students, 11 have a brother and 9 have a sister. There are 2 students who have a brother and a sister. What is the probability that a student has a sister
given that they have a brother?

Step-by-step explanation:

Conditional Probability

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:

step-by-step explanation:

milk=16 large

soda=280 kids

juice box=82 regular

63 soda +63 regular

124 large total

-362

step-by-step explanation:

(12)(4)+2(12)-34(12)+2(12)-3

  \/         \/         \/         \/

  48 +   24 -   408 + 24 - 3

      \   /               \   /

          72     -     432 - 3 = -363