NTA Abhyas JEE Main2020MathematicsSequences and SeriesPractice
If the tenth term of the sequence S = 1 + 5 + 13 + 29 + . … … . is k , then k 500 is equal to
Correct answer
4.09
Step-by-step solution
S = 1 + 5 + 13 + 29 + . … … + t 9 + t 10 S = . … … 1 + 5 + 13 + . … … . + t 8 + t 9 + t 10 Subtracting we get 0 = 1 + 4 + 8 + 16 + . … … 9 t e r m s - t 10 ⇒ t 10 = 1 + 4 + 8 + 16 + . … . . 9 t e r m s = 1 + 4 1 - 2 9 1 - 2 = 1 + 4 2 9 - 1 = 1 + 4 512 - 1 = 2045 ⇒ k = 2045 ⇒ k 500 = 4.09