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Unit Quiz: Probability 3 (Tree diagrams)

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Q1. Here is the first branch of a probability tree diagram.

Options:

  1. A
  2. B
  3. C
  4. D

Correct Answer:

  1. A

Q2. Here is the first branch of a different probability tree diagram. What should the missing probability be?

Options:

  1. 0.82
  2. 0.41
  3. 0.18
  4. 18

Correct Answer:

  1. 0.18

Q3. This tree diagram shows Amir taking red and blue counters from a jar. He replaces the counter after he has picked one up.

Options:

  1. A
  2. B
  3. C
  4. D

Correct Answer:

  1. C

Q4. For the probability tree shown, which calculation will find the probability of red followed by blue happening?

Options:

  1. 0.2 x 0.2
  2. 0.2 x 0.8
  3. 0.2 + 0.2
  4. 0.8 x 0.8

Correct Answer:

  1. 0.2 x 0.8

Q5. The probability that Amy and Joe win a game of chess is shown in the tree diagram. Work out the probability that over 2 games Amy wins twice.

Options:

  1. 0.09
  2. 0.6
  3. 0.9
  4. 0.49

Correct Answer:

  1. 0.09

Q6. James draws this probability tree diagram to help him calculate probabilities of taking sweets from a bag. What assumptions has James made when completing this probability tree?

Options:

  1. All probabilities add to 1 on each branch.
  2. He replaces the first sweet he takes.
  3. It doesn’t matter if he eats the first sweet he takes.

Correct Answer:

  1. He replaces the first sweet he takes.

Q7. Amy is going to pick 2 biscuits from a box. Some are chocolate and some are plain. The probability tree shows the probability information.

Options:

  1. A
  2. B
  3. C
  4. D

Correct Answer:

  1. A

Q8. James is also going to pick 2 biscuits from a box. Some are chocolate and some are plain. The probability tree shows the probability information.

Options:

  1. A
  2. B
  3. C
  4. D

Correct Answer:

  1. C

Q9. Here is a probability tree showing Amir taking red and blue sweets from a bag.

Options:

  1. P(R,R)
  2. P(R,B)
  3. P(B,R)
  4. P(B,B)

Correct Answer:

  1. P(B,R)

Q10. Probability of a dependent event is also called?

Options:

  1. Conditional probability.
  2. Biased probability.
  3. Random probability.
  4. Mutually exclusive.

Correct Answer:

  1. Conditional probability.

Q11. Simon has drawn this probability tree for a question on dependent probability. What mistake has he made?

Options:

  1. The fractions on each branch do not sum to 1.
  2. The second part of the probability tree has incorrect probabilities.
  3. The probabilities should be decimals.

Correct Answer:

  1. The second part of the probability tree has incorrect probabilities.

Q12. This tree diagram shows Amir taking red and blue sweets from a bag. He does not replace the sweet after he has taken one.

Options:

  1. A
  2. B
  3. C
  4. D

Correct Answer:

  1. C