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JEE Main202226 Jul 2022Morning ShiftMathematicsSequences and SeriesActual

The series of positive multiples of 3 is divided into sets : 3 , 6 , 9 , 12 , 15 , 18 , 21 , 24 , 27 , … Then the sum of the elements in the 11 th set is equal to _______.

Correct answer

0

Step-by-step solution

Given, 3 , 6 , 9 , 12 , 15 , 18 , 21 , 24 , 27 , ⋯ Now, the number of elements in 11 th  set will be = 1 + 10   2 = 21 The total number of elements up to 10 th set will be 1 + 3 + . . . + 19 = 10 2 = 100 ∴ elements in 11 th set = 3 · 101 , 3 · 102 ,   . . . . 3 · 121 Sum of these elements = 3 101 + 102 + ⋯ + 121 = 3 × 21 2 × 101 + 121 = 6993

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