# Unit Quiz: Probability 3 (Tree diagrams)

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

### Options:

- A
- B
- C
- D

### Correct Answer:

- A

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

### Options:

- 0.82
- 0.41
- 0.18
- 18

### Correct Answer:

- 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:

- A
- B
- C
- D

### Correct Answer:

- C

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

### Options:

- 0.2 x 0.2
- 0.2 x 0.8
- 0.2 + 0.2
- 0.8 x 0.8

### Correct Answer:

- 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:

- 0.09
- 0.6
- 0.9
- 0.49

### Correct Answer:

- 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:

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

### Correct Answer:

- 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:

- A
- B
- C
- D

### Correct Answer:

- 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:

- A
- B
- C
- D

### Correct Answer:

- C

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

### Options:

- P(R,R)
- P(R,B)
- P(B,R)
- P(B,B)

### Correct Answer:

- P(B,R)

## Q10. Probability of a dependent event is also called?

### Options:

- Conditional probability.
- Biased probability.
- Random probability.
- Mutually exclusive.

### Correct Answer:

- Conditional probability.

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

### Options:

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

### Correct Answer:

- 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:

- A
- B
- C
- D

### Correct Answer:

- C