15, 21, 39, 77, 143, (?) | vedclass

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(D) To find the missing number in the series $15, 21, 39, 77, 143, (?)$,we analyze the differences between consecutive terms:$21 - 15 = 6$$39 - 21 = 1

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$245$

Vedclass · Answer

(D) To find the missing number in the series $15, 21, 39, 77, 143, (?)$,we analyze the differences between consecutive terms:$21 - 15 = 6$$39 - 21 = 18$$77 - 39 = 38$$143 - 77 = 66$Now,analyze the differences of these differences:$18 - 6 = 12$$38 - 18 = 20$$66 - 38 = 28$Next,analyze the differences of the second-level differences:$20 - 12 = 8$$28 - 20 = 8$Since the third-level difference is constant $(8)$,we can continue the pattern:The next second-level difference will be $28 + 8 = 36$.The next first-level difference will be $66 + 36 = 102$.Therefore,the missing number is $143 + 102 = 245$.

$15, 21, 39, 77, 143, (?)$

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