options: Use permutations and combinations to compute probabilities of compound events and solve problems.

Apply the general Multiplication Rule in a uniform probability model, P(A and B) = P(A)P(B|A) = P(B)P(A|B), and interpret the answer in terms of the model.

Find the conditional probability of A given B as the fraction of B’s outcomes that also belong to A, and interpret the answer in terms of the model.

Apply the Addition Rule, P(A or B) = P(A) + P(B) – P(A and B), and interpret the answer in terms of the model.
problem_activity: Problem 1
Using the digits 1, 2, and 3, write an expression to answer the following questions
How many different three-digit numbers can you make when you can use each digit more than once?
How many different three-digit numbers can you make when you can only use each digit once?
Problem 2
Your phone requires you to use five numbers for the code, but you only can use numbers 1-5 for the code.
The first combination you come up with is:
| 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|
You then realize how "insecure" this number might be since anyone could guess it. Figuring this out you wonder, "How many possibilities are there for combinations if I only use each number once?"
Problem 3
You change the phone settings so that you only need a three-digit code to open the lock.
This means you have 5 numbers to choose from and 3 positions to put those numbers in, which is represented by
$$_5P_3$$
. How many different combinations can you get if you have three positions and a choice of five numbers with no repetition?


correct_option_index: 0