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Find the sum of first 22 terms of an AP in which d = 7 and 22nd term is 149. |
Answer» d = 7, a22 = 149, S22 = ? a = a + (n – 1)d a + (22 – 1)7 = 149 a + 21 × 7 = 149 a + 147 = 149 =149 – 147 ∴ a = 2 ∴ Sn = \(\frac{n}{2}\)[a + an] S22 = \(\frac{22}{2}\)[2 + 149] = 11[151] ∴ S22 = 1661 |
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