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Inclusion Exclusion

How many integers between 1 and 1200 are NOT multiples of any of the numbers 2, 3 or 5?

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Weekly Problem 27 - 2011

Pizza, Indian or Chinese takeaway. Each teenager from a class only likes two of these, but can you work which two?

One or Both

Stage: 3 Challenge Level: Challenge Level:2 Challenge Level:2

Why not try some different class sizes first?

As 60% of the group got one question correct and 70% the other what does this tell you about the percentage that got both right?