1. What fraction should go here
3 8
What fraction should go here

2. Why is this fraction ?

3. A red marble has been removed
3 8

4. So now there are 7 marbles, 4 of which are red
3 8

5. What fraction should go here? Why?
3 7
What fraction should go here?
Why?
3 8

6. This time, a green marble has been removed and not replaced
3 7
3 8

7. What should these two fractions be?
3 7
What should these two fractions be?
Why?
3 8

8. What should these two fractions be?
3 7
What should these two fractions be?
Why?
5 7
3 8
2 7

9. We can now answer questions using this tree diagram.
3 7
5 7
3 8
2 7

10. What is the probability of picking two red marbles?
On your whiteboards:
What is the probability of picking two red marbles?
5 8 × 4 7
3 7
5 7
3 8
2 7

11. What is the probability of picking two green marbles?
On your whiteboards:
What is the probability of picking two green marbles?
3 7
5 7
3 8 × 2 7
3 8
2 7

12. What is the probability of picking marbles of different colours?
On your whiteboards:
What is the probability of picking marbles of different colours?
3 7
5 8 × 3 7
5 7
3 8
2 7

13. What is the probability of picking marbles of different colours?
On your whiteboards:
What is the probability of picking marbles of different colours?
But we can also have…
3 7
5 8 × 3 7
5 7
3 8 × 5 7
3 8
2 7