To work out the chance (probability) for a single branch we multiply each branch that makes up the path.
In the example above the chance of picking a blue ball (2/5) followed by another blue ball (1/4) is found by multiplying 2/5 by 1/4.
The answer 2/20 (or 1/10) is the chance of picking two blue balls in a row.
Questions
a) What is the chance of picking a blue ball followed by a red ball?
b) What is the chance of picking a red ball followed by a blue ball?
c) What is the chance of picking two red balls?
Answers
a) 2/5 x 3/4 = 6/20 or 3/10
b) 3/5 x 2/4 = 6/20 or 3/10
c) 3/4 x 2/4 = 6/20 or 3/10
In the example above the chance of picking a blue ball (2/5) followed by another blue ball (1/4) is found by multiplying 2/5 by 1/4.
The answer 2/20 (or 1/10) is the chance of picking two blue balls in a row.
Questions
a) What is the chance of picking a blue ball followed by a red ball?
b) What is the chance of picking a red ball followed by a blue ball?
c) What is the chance of picking two red balls?
Answers
a) 2/5 x 3/4 = 6/20 or 3/10
b) 3/5 x 2/4 = 6/20 or 3/10
c) 3/4 x 2/4 = 6/20 or 3/10
The same process applies if the chance is written in decimal numbers. In the example above the chance of Sam being chosen followed by him saying Yes is 0.6 x 0.5 = 0.3 (or 30%).
Questions
a) What is the chance of arriving 'on time' and the dinner is NOT burnt?
b) What is the chance of arriving 'on time' and the dinner IS burnt?
c) What is the chance of arriving 'late' and the dinner IS burnt?
Answers
a) 0.7 x 0.9 = 0.63 (or 63%)
b) 0.7 x 0.1 = 0.07 (or 7%)
c) 0.3 x 0.8 = 0.24 (or 24%)
a) What is the chance of arriving 'on time' and the dinner is NOT burnt?
b) What is the chance of arriving 'on time' and the dinner IS burnt?
c) What is the chance of arriving 'late' and the dinner IS burnt?
Answers
a) 0.7 x 0.9 = 0.63 (or 63%)
b) 0.7 x 0.1 = 0.07 (or 7%)
c) 0.3 x 0.8 = 0.24 (or 24%)