Let S= 1,2,3,4,5,6,9 . Then the number of elements in the set T= A S:A and the sum of all the elements of A is not a multiple of 3 is (JEE Main 2023)

JEE Main Mathematics question

Let . Then the number of elements in the set is (JEE Main 2023)

Answer: 80

Residues mod 3: , , . Choosing elements from and from with $i≡

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Question ID VK-003284