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1.
1+2+3+4+------+18= কত?
- A. 168
- B. 168
- C. 168
- D. 168
Answer: Option B
Explanation:
এখানে, মোট পদ n = 18
∴ সমষ্টি S = n(n + 1)/2
= 18(18 + 1)/2
= (18×19)/2
= 171
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