Forum - Algebra

Heavy exercise: No. of subsets of a set

Iorgu
Visitor
2016-01-12 03:17:28
#1
Hi,

I need to know this problem for an exam.
Let's find out n (natural number) for which the set {1, 2, 3, ... , n} has exactly 120 subsets , 2 element subsets.

 

RE: Heavy exercise: No. of subsets of a set

IanTeach
Visitor
2016-01-12 05:34:42
#2

The number of the a elements subsets of a set with n elements is given by combinations. So though, we got:

RE: Heavy exercise: No. of subsets of a set

IanTeach
Visitor
2016-01-12 05:36:21
#3

no of substes of a set with n elements



So,

RE: Heavy exercise: No. of subsets of a set

IanTeach
Visitor
2016-01-12 05:37:17
#4


n2-n-240=0

You have to solve this eqution n.


 

 
 

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