CA Foundation · Quantitative Aptitude · Sequence and Series
The sequence 2, 6, 12, 20, 30, ... has its nth term equal to n(n+1). Which term of this sequence equals 240?
Since the nth term is n(n+1), setting it equal to 240 gives n = 15 because 15 × 16 = 240. Hence 240 is the 15th term of the sequence.
- A14th
- B16th
- C15thCorrect
- D240th
Explanation
Set n(n+1) = 240, so n² + n − 240 = 0. Factorising gives (n − 15)(n + 16) = 0, so n = 15 (positive). Check: 15 × 16 = 240. The 16th term is 16 × 17 = 272, so 16th is wrong.
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