1. Tree Diagrams – Unconditional – Demonstration
This resource provides animated demonstrations of the mathematical method.
Check animations and delete slides not needed for your class.

2. John flips a coin and Jane rolls a dice.
These are independent events.
What is the probability the result is tails and a 6?
Coin Flip
Dice Roll
Results
1 6
1 2 × =
1 12 6 H6
Heads AND a 6 H
1 2
5 6
1 2 × =
5 12
1-5
H1-5
1 6
1 2 × =
1 12 6 T6
1 2 T
5 6
1 2 × =
5 12
1-5
T1-5

3. Unconditional Tree Diagrams
To win the league, Burham United need to win against
Wedly Wanderers & then Rexham Rovers.
Unconditional Tree Diagrams ①
The probability of winning again Wedly is 2 3
The probability of winning again Rexham is 3 4
What is the probability Burham win the league (win both matches)?
Vs. Wedley
Vs. Rexham
Result
3 4
2 3 × 3 4 = 6 12
P(WW) =
Win WW
2 3
Win
2 3 × 1 4 = 2 12
1 4
Lose WL
3 4
1 3 × 3 4 = 3 12
Win LW
1 3
Lose
1 3 × 1 4 = 1 12
1 4
Lose LL

4. The probability it is sunny on Saturday is 3 7②
The probability it is sunny on Sunday is 2 5
What is P(not sunny all weekend)?
Saturday
Sunday
Result
2 5
3 7 × 2 5 = 6 35
Sunny SS
3 7
Sunny
3 7 × 3 5 = 9 35
3 5
Not
Sunny SN
2 5
4 7 × 2 5 = 8 35
Sunny NS
4 7
Not
Sunny
4 7 × 3 5 = 12 35
3 5
Not
Sunny
P(NN) = NN

5. There are black and white marbles in the box.③
Box & Marbles
One is picked – and replaced – then another is picked.
What is the probability both picks are the same colour?
P (BB or WW) = =
1st Pick
2nd Pick
Result
3 10
3 10 × = 9 100
Black BB
3 10
Black
3 10 × =
7 10
White BW
3 10
7 10 × =
Black WB
7 10
White
7 10 × =
7 10
White WW

6. ④
The probability Jill passes her Geography test is 0.8
The probability Jill passes her Science test is 0.4
What is the probability she passes only one of the tests?
P(PF or FP) = = 0.56
Geography Test
Science Test
Result
0.4
Pass PP
0.8 ×0.4=0.32
Pass
0.8
0.6
Fail PF
0.8 ×0.6=0.48
0.4
Pass FP
0.2 ×0.4=0.08
0.2
Fail
Fail FF
0.2 ×0.6=0.12
0.6

7. A coin and a dice were thrown.
What is the possibility of getting
a Tails and a 6?
What did Mary do wrong?
1st Event
2nd Event
Results
1 6
1 2 x =
1 12
1-5
T1-5
1 2 T
1 2 x =
2 12
1 6 6 T6
5 6
1 2 x =
6 12
1-5
H1-5
1 2 H
1 2 x =
5 12
5 6 6 H6

8. A coin and a dice were thrown.
What is the possibility of getting
a Tails and a 6?
What did Mary do wrong?
1st Event
2nd Event
Results
1 6
1 2 x =
1 12
1-5
T1-5
1 2 T
1 2 x =
2 12
1 6 6 T6
5 6
1 2 x =
6 12
1-5
H1-5
1 2 H
1 2 x =
5 12
5 6 6 H6

11. tom@goteachmaths.co.uk Questions? Comments? Suggestions?
…or have you found a mistake!?
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