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If the ratio of the sum of the first n terms of two A.Ps is (7n + 1) : (4n + 27), then find the ratio of their 9th terms. |
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Answer» n :-If the ratio of the sum of the first n terms of two A.Ps is (7n + 1) : (4N + 27), then find the ratio of their 9th terms.Solution :- Sn = n/2 {a1 + (n - 1)d1}Sn' = n/2 { a2 + (n - 1) d2}a1 + (n - 1) d1 / a2 + (n - 1) d2 = 7n + 1 / 4n + 27In order to find nth term, we have to replace n by 2m - 1a1 + (2m - 1) d1 / a2 +(2m -1)/ d2 = 7(2m - 1) + 1/ 4(2m -1) + 27= 14m - 7 + 1/ 8m - 4+27= 14m - 6/ 8m + 23Now replace m by 9 to get the ratio of 9th term= 14(9) - 6/ 8(9) + 23= 120/95= 24/19.Notebook solution : Click to the attachment. |
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