11yeah it's (c)
If x = {1,2,3,..............., 100} and let S = {(a,b,c) | a,b,c belongs to a < b and a <c }, then the number of elements in S are :
(a) 328250 (b) 328450 (c)328350 (d) none
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5 Answers
341Consider the subsets of X with three elements.
Of these 1/3 rd have this property
3EXP. GOES LIKE THIS .......
i can select 3 elements ...
case 1 ..
3 distinct elements ...
total no. of ways ..
100C3 ...
now these three elements i can arrange in such a way that a<b<c
or a<c<b
hence total ways .... 2(100C3) ..
case 2 ..
2 elements same ...
total ways ..
100C2 ...
i can arrange each set picked only in 1 way
case1+case2 = 100C2 + 2(100C3) ....
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