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| 1. |
Find the middle term of sequence 7,13,19,......,241 |
| Answer» Given A.P :-\xa07,13,19,........241\xa0∴a=7\xa0tn\u200b=241\xa0d=13−7=6\xa0∴tn\u200b=a+(n−1)d\xa0∴241=7+(n−1)6\xa0∴6241−7\u200b=n−1\xa0∴6234\u200b=n−1∴39+1=n;n=40\xa0∴2n\u200b=240\u200b=20......(middle term)\xa0∴2n\u200b+1=21\xa0.....(middle term)∴t20\u200b=7+(20−1)6\xa0∴t20\u200b=7+19×6\xa0∴t20\u200b=7+114=121\xa0∴t21\u200b=121+6=127\xa0∴ Middle terms are\xa0121\u200b\xa0and\xa0127\u200b. | |