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An important strategy in answering probability questions requires us to consider whether it is easier to work out the probability of an event occurring or the probability of it NOT occurring. In this problem, learners are introduced to tree diagrams and the concept of mutually exclusive events whose probabilities sum to 1
Ask the introductory question:
"Imagine flipping a coin three times. What's the probability you will get a head on at least one of the flips?"
Finally, the remaining questions from the problem can be used with the class to consolidate these ideas.
What is the probability of getting at least one head?
What is the probability of getting no heads?
Spend some time working together as a class on listing probabilities, and then move to the tree diagram representation simply as an efficient way of listing systematically.
You can read about some of the issues which might arise when teaching probability in this article.
Same Number! provides a natural extension to this problem.
Your partner chooses two beads and places them side by side behind a screen. What is the minimum number of guesses you would need to be sure of guessing the two beads and their positions?
Discs are flipped in the air. You win if all the faces show the same colour. What is the probability of winning?
Are these games fair? How can you tell?