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1. 11 + 18 + 25 + 32 + .........ধারাটির 15টি পদের সমষ্টি কত?
- A. 900
- B. 900
- C. 900
- D. 900
Answer: Option A
Explanation:
It is an arithmetic series.
We know,
Sn = n/2{2a + (n - 1)d}
S15 = 15/2{2x11 + (15 - 1)7} = 7.5{22 + 98} = 900
We know,
Sn = n/2{2a + (n - 1)d}
S15 = 15/2{2x11 + (15 - 1)7} = 7.5{22 + 98} = 900
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