If 85% of people have a bowl of cereal for breakfast, 60% of people have some toast for breakfast, and 50% of people have both cereal and toast for breakfast, what proportion of people have neither cereal nor toast for breakfast?

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- January 30th 2009, 09:14 AMmitch_nufcStats question
If 85% of people have a bowl of cereal for breakfast, 60% of people have some toast for breakfast, and 50% of people have both cereal and toast for breakfast, what proportion of people have neither cereal nor toast for breakfast?

- January 30th 2009, 09:21 AMredwing
Maybe this equation can help (it's called the inclusion-exclusion principle):

n(R union S) = n(R) + n(s) - n(R intersection S)

Note: drawing venn diagrams helps too a lot of times - January 30th 2009, 09:24 AMmitch_nufc
The only problem is, I've never done stats in my life :|... I can do pure math, applied math etc very well, but the last time i done stats was about 5 years ago so im sort of learning everything by scratch to be able to tackle these questions

- January 30th 2009, 09:26 AMGreenb
If 50% are having both cereal and toast it means that of the 85% eating cereal only 35% are eating just that.

Same goes for the toast, of the 60% eating toast only 10% are eating just that leaving 55% eating neither. - January 30th 2009, 09:29 AMmitch_nufc
Thanks for all your replies but I cant see how I can form a formal arguement to do these questions? :( How would the working to the solution of this problem go? :S

- January 30th 2009, 09:33 AMGreenb
When your dealing with these kind of problems the solution is mostly displayed in a venndiagram graphicly.

Venn diagram