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TS EAMCET · Maths · Sequences and Series

If 11·5+15·9+19·13+ to n terms =27109 then n=

  1. A 21
  2. B 27
  3. C 63
  4. D 189
Verified Solution

Answer & Solution

Correct Answer

(B) 27

Step-by-step Solution

Detailed explanation

Given 11·5+15·9+19·13+… to n terms =27109. We know that the nth term of an A.P., a, a+d, a+2d,... is a+n-1d. Hence, the nth term of 1, 5, 9,... is 1+n-14=4n-3 and that of 5, 9, 13,... is 5+n-14=4n+1. Thus, the given series…