What is the next number in the sequence 4, 13, 28, 49, 76, 109, ... ?

Answer and explanation

Correct answer: C. 148

  1. Step 1: Find the differences: 9, 15, 21, 27, 33. Step 2. The differences themselves go up by 6 each time, so the next difference is 39. Step 3. 109 + 39 = 148. The rule is 3n² + 1. Answer: 148. Why not the others: 142: This repeats the last difference of 33 instead of increasing it. 143: This increases the difference by 1 instead of by 6. 154: This increases the difference by 12 instead of by 6.

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