Question

Your Algebra 2 class has 20 students. 4 students are to be chosen at random for a project.

A. How many groups of four are possible?

B. You are in the Algebra 2 class with 3 other friends. What is the probability that the four of you are chosen?

Answer 1

4845

.020639% (or 1/4845)

Explanation:

For the first one we have to use combinations (because the order doesn't matter)

The formula is as follows:

for ACB

`(A!)/((A-B)!*B!)\\\\(20!)/((20-4)!*4!)=4845`

2.

for probabilty the odds of an outcome is just: number of times the requirement is satisfied/total number of possibliites

we know that there are 4845 possbile groups and only one in which we get all of our friends so it's just

1/4845= .020639%

Answer 2

A. 5 groups

Explanation:

You would use multiplication for this. just think what does 4 × _ = 20? well 5! since four times give is twenty.