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If The 6th term of an a.p 37 and the sum of the first term is 147, find the ,first term And fifteen term |
Answer» Correct Question:-If the 6th term of an AP is 37 and the sum of first 6 terms is 147 , find the first term and sum of first 15 terms. Answer:-Given: 6th term of an AP = 37 We know that, nth term of an AP (a_n) = a + (N - 1)d → a + (6 - 1)d = 37 → a + 5d = 37 -- equation (1) And also given that, Sum of first 6 terms (S_6) = 147 Sum of first n terms of an AP = n/2 * [ a + L (nth term)] → 6/2 * [ a + (37) ] = 147 → 3(a + 37) = 147 → 3a + 111 = 147 → 3a = 147 - 111 → 3a = 36 → a = 36/3 → a = 12Substitute "a" value in equation (1). → 12 + 5d = 37 → 5d = 37 - 12 → 5d = 25 → d = 25/5 → d = 5→ 15TH term = 12 + (15 - 1)(5) → a_15 = 12 + 70 → a_15 = 82Sum of first 15 terms = 15/2 * [12 + 82 ] → S_15 = 15/2 * (94) → S_15 = 705Hence, the first term of the given AP is 12 and the sum of first 15 terms is 705. |
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