We have the following sets:

X=(a,b,c,d)∈S:b<c<d,

Y=(a,b,c,d)∈S:a<c<d,

Z=(a,b,c,d)∈S:a<b<d,

F=(a,b,c,d)∈S:a<b<c,

Where each of a,b,c,d have integer values from 1 to 5

How to calculate |X∩Y|, |X∩Z|, |Z∩F|, |X∩Y∩Z|, |X∩Y∩Z∩F| without the need to write down all possible combinations

## how to calculate these intersections without having to write

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### Re: how to calculate these intersections without having to w

Is this homework?

Can you see which of the sets are equal to each other?

Can you see which of the sets are equal to each other?

wee free kings

- jestingrabbit
- Factoids are just Datas that haven't grown up yet
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### Re: how to calculate these intersections without having to w

if x is in A∩B, the x is in A and x is in B. If A is all the things that satisfy conditionA, and B is all the things that satisfy conditionB, then x satisfies both conditionA and conditionB. That's all you really need.

ameretrifle wrote:Magic space feudalism is therefore a viable idea.

### Re: how to calculate these intersections without having to w

The first and third of these sets have equal size, and there's a nice bijection between them, if you can spot it.

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