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Question: Answered & Verified by Expert
Let $S=\{0,1,2,3, \ldots, 100\}$. The number of ways of selecting $x, y \in S$ such that $x \neq y$ and $x+y=100$ is
MathematicsPermutation CombinationAP EAMCETAP EAMCET 2018 (23 Apr Shift 1)
Options:
  • A 51
  • B 40
  • C 50
  • D 100
Solution:
1235 Upvotes Verified Answer
The correct answer is: 50
Let $S=\{0,1,2,3, \ldots, 100\} x, y \in s$.
and
$$
x+y=100
$$
If $x=0$,
$y=100$
$x=1$,
$y=99$
$x=49 \Rightarrow y=51$
In this way, the total pairs in 50 .
So, the number of required ways $=50$

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