If the sum of the first 40 terms of the series, 3 + 4 + 8 + 9 + 13 + 14 + 18 + 19 + . . . . is 102 m , then m is equal to

Question

If the sum of the first 40 terms of the series, 3 + 4 + 8 + 9 + 13 + 14 + 18 + 19 + . . . . is 102 m , then m is equal to, 20, 25, 5, 10

MARKS App · Accepted Answer

S = 3 + 4 ⏟ + 8 + 9 ⏟ + 13 + 14 ⏟ + 18 + 19 ⏟ … 40 terms S = 7 + 17 + 27 + 37 + 47 + … 20 terms S 40 = 20 2 2 × 7 + 19 10 = 10 14 + 190 = 10 2040 = 102 20 ⇒ m = 20

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