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

If the sum of the first 40 terms of the series, 3+4+8+9+13+14+18+19+.... is 102m,  then  m is equal to
  1. 20
  2. 25
  3. 5
  4. 10

Solution

S=3+4⏟+8+9⏟+13+14⏟+18+19⏟…40 terms
S=7+17+27+37+47+…20 terms
S40=2022×7+1910=1014+190=102040=10220
⇒m=20

Asked in: JEE Main 2020 (07 Jan Shift 2)

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