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Lesson 14: Determining the Theoretical Probability of an Event — Practice Questions

  1. 1. A desk drawer contains 6 black pens, 4 blue pens, and 5 red pens. If one pen is chosen at random, what is the probability it is blue? Express your answer as a fraction. ___

  2. 2. A standard six-sided number cube is rolled. What is the theoretical probability of rolling a number greater than 4?

    • A. $\frac{1}{6}$
    • B. $\frac{1}{3}$
    • C. $\frac{2}{3}$
    • D. $\frac{1}{2}$
  3. 3. A spinner has 8 equal sections numbered 1 through 8. What is the probability of the spinner *not* landing on the number 7? Express your answer as a fraction. ___

  4. 4. In the formula for theoretical probability, what does the numerator represent?

    • A. The total number of outcomes
    • B. The number of unfavorable outcomes
    • C. The number of favorable outcomes
    • D. The probability of a single outcome
  5. 5. A box contains 5 glazed, 3 chocolate, and 6 jelly donuts. If one donut is selected at random, what is the probability it is either chocolate or jelly? Express your answer as a fraction. ___

  6. 6. The probability of a flight being delayed is $0.15$. What is the probability that the flight is *not* delayed? The answer is ___.

  7. 7. A bag contains 3 red marbles and 9 green marbles. If you pick one marble without looking, what is the probability it is *not* red?

    • A. $\frac{1}{4}$
    • B. $\frac{3}{4}$
    • C. $\frac{1}{3}$
    • D. $\frac{2}{3}$
  8. 8. A local weather station reports a 40% chance of rain. What is the percent chance that it will *not* rain?

    • A. 40%
    • B. 60%
    • C. 100%
    • D. 140%
  9. 9. A spinner is divided into 8 equal sections. The probability of landing on a blue section is $\frac{3}{8}$. What is the probability of *not* landing on a blue section? Express your answer as a fraction: ___.

  10. 10. Let $\operatorname{P}(E)$ be the probability of an event $E$. Which expression correctly represents the probability of the complement of event $E$?

    • A. 1 + \operatorname{P}(E)
    • B. 1 - \operatorname{P}(E)
    • C. \operatorname{P}(E) - 1
    • D. $\frac{1}{\operatorname{P}(E)}$