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Question 5fh term of an arithmetic progression are 10 and 96 respectively.Find the first term and the common difference and hence find the sum of the first15 terms. |
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Answer» let first term be a and common Difference be dSo, According to questiona(2) = 10a(45) = 96 a + d = 10 ......(1)a + 44d = 96 .....(2)eq(2) - eq (1) 43d = 86d = 2So, from (1) a = 8Sum of First 15 term ,S(n) = n(2a+(n-1)d)/2S(15) = 15/2 ( 16 + 14×2)S(15) = 15/2 (16+ 28) = 15/2 × 44 = 330 |
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