Multiple choice

Directions: In the following series, one of the terms given is wrong. Find the incorrect term and mark that as your answer. 218 154 105 68 44 28 19

  1. 68

  2. 19

  3. 154

  4. 105

  5. None of these
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A Correct answer
Explanation

The differences are: 218-154=64, 154-105=49, 105-68=37, 68-44=24, 44-28=16, 28-19=9. The pattern of differences should be squares (8^2, 7^2, 6^2, 5^2, 4^2, 3^2). 105-68 should be 36, so 105-36 = 69. If 69 were there, 69-44=25 (5^2). Thus 68 is the incorrect term.

AI explanation

The series decreases by subtracting perfect cubes in descending order: 64, 27, 8, 1. Subtracting 4 cubed from 218 gives 154, subtracting 3 cubed from 154 gives 105, subtracting 2 cubed from 105 gives 97, subtracting 1 cubed from 97 gives 44, subtracting 0 cubed from 44 gives 28, and subtracting negative 1 cubed from 28 gives 19. The number 68 is the incorrect term because it should be 97.

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