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Basic Probability Word Problems Practice Questions

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Updated on Oct 3, 2011

To review these concepts, go to Basic Probability Word Problems Study Guide.

Basic Probability Word Problems Practice Questions

Practice 1

Problems

  1. Charles is spinning a spinner like the one shown in the figure while he is playing a game.
  2. FINDING THE PROBABILITY THAT AN EVENT WILL NOT HAPPEN

    What is the probability that he spins a 5 on his next turn?

  3. The letters from the word GEOMETRY are placed in a hat. What is the probability of selecting an M when you are choosing one letter without looking?
  4. What is the probability of getting a 7 when you are rolling a number cube?
  5. If the probability that it will rain is , then what is the probability that it will not rain?
  6. When you are selecting a number at random from the digits 0–9, what is the probability of not selecting a 3?

Solutions

  1. Read and understand the question. This question is looking for the probability of getting a 5 when you are spinning a spinner. There are 6 equal sections to the spinner.
  2. Make a plan. Use the fact that there are 6 equal sections and 1 of the sections is labeled with a 5. Substitute into the formula

    .

    Carry out the plan. The formula becomes P(5) = The probability is equal to

    Check your answer. To check this answer, substitute the values again to see if the answer is reasonable. Since 1 out of the 6 sections is labeled with a 5, the probability is equal to This answer is checking.

  3. Read and understand the question. This question is looking for the probability of selecting a letter M from the word GEOMETRY.
  4. Make a plan. Use the facts that there are 8 letters in the word and 1 is a letter M. Substitute into the formula

    .

    Carry out the plan. The formula becomes P(M) = The probability is equal to

    Check your answer. To check this answer, substitute the values again to see if the answer is reasonable. Since 1 out of the 8 letters in the word is the letter M, the probability is equal to This answer is checking.

  5. Read and understand the question. This question is looking for the probability of rolling a 7 on a number cube. There are 6 sides on a number cube.
  6. Make a plan. Use the fact that there are 6 sides on the number cube and none of the sides have 7 dots. Substitute into the formula

    .

    Carry out the plan. The formula becomes P(7) = = 0. The probability is equal to 0.

    Check your answer. This was an example of an impossible event. Thus, the probability is equal to 0. This answer is checking.

  7. Read and understand the question. This question is looking for the probability that it will not rain when the probability that it will rain is given.
  8. Make a plan. Use the fact that the probability that it will rain is Substitute into the formula P(not E) = 1 – P(E).

    Carry out the plan. The formula becomes P(not rain) = The probability is equal to

    Check your answer. To check this answer, add the probability that it will rain to the probability that it will not rain. Make sure that the sum is equal to This answer is checking.

  9. Read and understand the question. This question is looking for the probability of not selecting a 3 from the digits 0 – 9. There are 10 digits from 0 to 9.
  10. Make a plan. Use the fact that the probability of selecting a 3 is Substitute into the formula P(not E) = 1 – P(E).

    Carry out the plan. The formula becomes P(not 3) = The probability is equal to

    Check your answer. To check this answer, add the probability of selecting a 3 with the probability of not selecting a 3, and make sure that the sum is equal to This answer is checking.

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