Paper 1 · Mathematical Reasoning and Aptitude
UGC NET December 2021 June 2022 (09.07.2022) Shift-II
Find the wrong term in the series: 7, 28, 63, 124, 215, 342, 511
A28 ✓ Correct
B63
C342
D511
Correct answer: (A) 28 — The wrong term in the series is 28.
Explanation
★The wrong term in the series is 28.
★Each term follows the pattern of a cube minus one.
★2 cubed minus 1 is 7, and 3 cubed minus 1 is 26, not 28.
★4 cubed minus 1 is 63, and 5 cubed minus 1 is 124.
★6 cubed minus 1 is 215, 7 cubed minus 1 is 342, and 8 cubed minus 1 is 511.
★So the second term should be 26, making 28 the wrong term.
★Cube based series are spotted by testing n cubed plus or minus a constant.
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