CA Foundation · Quantitative Aptitude · Sequence and Series
A sequence is defined by T1 = 3 and Tn = 2×T(n-1) - 1 for n ≥ 2. What is the value of T5?
T5 equals 33. Applying the rule repeatedly from T1 = 3 gives T2 = 5, T3 = 9, T4 = 17 and then T5 = 2 × 17 - 1 = 33. The pattern also fits the formula 2 to the power n plus 1.
- A33Correct
- B31
- C17
- D65
Explanation
T2 = 2×3 - 1 = 5; T3 = 2×5 - 1 = 9; T4 = 2×9 - 1 = 17; T5 = 2×17 - 1 = 33. Check: Tn = 2^n + 1 gives 2^5 + 1 = 33. The value 17 is T4, a one-step slip.
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