Q. Find the least value of n for which 1 + 3+3+ ...................3n-1 > 1000.

Dear Student,


1+3+32+33....3n-1>1000Now this a GP with common ratio r=3Now apply sum of GP formula30×3n-13-1>10003n-1>20003n>2001now the least value of n which satisfies this inequality is 37=2187>2001Hence answer is n=7

Regards,

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