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1. 1+3+5+7+9+.........+51= কত?
- A. 676
- B. 676
- C. 676
- D. 676
Answer: Option A
Explanation:
1 + 3 + 5 + 7 + 9 + - - - - + 51
১ম পদ, a = 1
সাধারণ অন্তর, d = 3~1 = 2
শেষ পদ = 51
a + (n~1)d = 51
বা, 1 + (n~1)2 = 51
(n~1)2 = 50
বা, n~1 = 50/2
বা, n~1 = 25
বা, n = 25 + 1 = 26
সুতরাং সমষ্টি, S = n/2{2a + (n~1)d
= 26/2{2.1 + (26 - 1)2}
= 13{2 + 50} = 13×52 = 676 |
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