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ICSE Class 10 Answered

the sum of first 6 terms of an A.P is 63 .The ratio of the 10th term to the 20th term is 1:2 . calculate the first and the 15th terms
Asked by savithakotari962 | 08 Feb, 2021, 08:40: PM
Expert Answer
S subscript 6 equals 63 6 over 2 open square brackets 2 a plus 5 d close square brackets equals 63 2 a plus 5 d equals 21 minus negative negative negative negative negative negative negative left parenthesis 1 right parenthesis a subscript 10 over a subscript 20 equals fraction numerator a plus 9 d over denominator a plus 19 d end fraction 1 half equals fraction numerator a plus 9 d over denominator a plus 19 d end fraction a plus 19 d equals 2 a plus 18 d a equals d P u t t i n g space t h i s space i s space e q u a t i o n space left parenthesis 1 right parenthesis 7 d equals 21 d equals 3 a l s o space a equals 3 15 t h space t e r m space i s space g i v e n space b y a subscript 15 equals a plus 14 d equals 3 plus 14 space x space 3 equals 45
Answered by Utkarsh Lokhande | 17 Feb, 2021, 10:15: AM

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