What number should replace the question mark in the series: 125, 129, 120, 136, 111, 147, ?
A183
B258
C196
D98 ✓ Correct
Correct answer: (D) 98
Explanation
The missing number is 98.
The differences alternate in sign and grow as squares.
+2^2, -3^2, +4^2, -5^2, +6^2 give 129, 120, 136, 111, 147.
The next step is -7^2 = -49.
147 - 49 = 98.
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