JEE MATHEMATICS MCQ: PERMUTATIONS

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Application +4 | -1

The total number of ways of selecting two numbers from the set

\{1,2,3,4, \ldots, 3 n\}

, so that their sum of divisible by 3, is

View answer and explanation

Correct option: B

\frac{3 n^2-n}{2}

Option B (

\frac{{3 n^2-n}}{{2}}

) is correct because it accounts for selecting two numbers from the same remainder group modulo 3 or one number from each of the two different remainder groups.

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