There is a 70% probability that a pupil who uses the swimming pool and gym will be selected. How do I know this? Well, since 30 pupils use neither, this means at least 50/80 pupils use both. This reduces to 5/8, so 5/8 pupils use both the gym and swimming pool. 5/8 as a decimal is equal to 70%, because 80% would be 6/8, 90% would be 7/8, and 100% would be 8/8.
That’s one way to do it.
Another way to solve this is as follows:
Since 22 pupils use the swimming pool and 34 use the gym, that means 56 pupils use both total. 56/80 reduces to 7/10, which as a decimal is 70% or 0.7.
Your final answer: Probability = 70%
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