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Question
(5 + 13 + 21 + ... + 181) = ?
Options
2476
2337
2219
2139
MCQ
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Solution
2139
Explanation:
Let the number of terms be n.
Then, Tn = 181.
∴ 5 + (n – 1) × 8 = 181
⇒ (n – 1) × 8 = 176
⇒ (n – 1) = 22
⇒ n = 23
∴ Sum = `n/2 (a + l)`
= `23/2 (5 + 181)`
= `23/2 (186)`
= 23 × 93
= 2139
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