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sets

by [email protected] » Mon Mar 02, 2009 12:07 pm
400 people join the local gym. 60 people take aerobics, 60 people take yoga. Of these, 30 people take both aerobics and yoga. if a customer is chosen at random from the gym, what is the probability that customer takes aerobics or yoga but not both?


[spoiler]3/20[/spoiler]
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by dendude » Mon Mar 02, 2009 2:28 pm
60 take yoga and 60 take aerobics.
And 30 take both, meaning 30 take yoga only, 30 take aerobics only and 30 take both.

The required probability would be, 30/400 + 30/400
= (2*30)/400
= 3/20
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Re: sets

by iwant700plus » Mon Mar 02, 2009 2:46 pm
The best way is to draw two sets that intersect (see my attachment). It's easy to visualize that what you are looking for is the area outside of the intersection which is given by

30/400+30/400=3/20

[email protected] wrote:400 people join the local gym. 60 people take aerobics, 60 people take yoga. Of these, 30 people take both aerobics and yoga. if a customer is chosen at random from the gym, what is the probability that customer takes aerobics or yoga but not both?


[spoiler]3/20[/spoiler]
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