basic probability review worksheet - fall 2025\na 6 - sided die is rolled one time. find:\n1. p(roll a…

Explanation:

Step1: Recall probability formula

The probability formula is $P(A)=\frac{n(A)}{n(S)}$, where $n(A)$ is the number of favorable outcomes and $n(S)$ is the total number of outcomes.

Step2: Solve for P(7) (Question 19)

There is 1 favorable outcome (the number 7) and 20 total outcomes (numbers from 1 - 20). So $P(7)=\frac{1}{20}$.

Step3: Solve for P(6 or lower) (Question 20)

The favorable outcomes are 1, 2, 3, 4, 5, 6. So $n(A) = 6$ and $n(S)=20$. Then $P(6\text{ or lower})=\frac{6}{20}=\frac{3}{10}$.

Step4: Solve for P(18 or higher) (Question 21)

The favorable outcomes are 18, 19, 20. So $n(A)=3$ and $n(S) = 20$. Then $P(18\text{ or higher})=\frac{3}{20}$.

Step5: Solve for P(multiple of 4) (Question 22)

The multiples of 4 from 1 - 20 are 4, 8, 12, 16, 20. So $n(A)=5$ and $n(S)=20$. Then $P(\text{multiple of }4)=\frac{5}{20}=\frac{1}{4}$.

Step6: Solve for P(9 or 11) (Question 23)

There are 2 favorable outcomes (9 and 11) and 20 total outcomes. So $P(9\text{ or }11)=\frac{2}{20}=\frac{1}{10}$.

Step7: Solve for P(not a 15) (Question 24)

The number of non - 15 outcomes is $20 - 1=19$. So $P(\text{not a }15)=\frac{19}{20}$.

Step8: Solve for P(21) (Question 25)

There are 0 favorable outcomes (21 is not in the range 1 - 20) and 20 total outcomes. So $P(21)=0$.

Answer:

19. $\frac{1}{20}$
20. $\frac{3}{10}$
21. $\frac{3}{20}$
22. $\frac{1}{4}$
23. $\frac{1}{10}$
24. $\frac{19}{20}$
25. $0$