📢 Too many exams? Don’t know which one suits you best? Book Your Free Expert 👉 call Now!

  • google app store apple app store

    • Question

      Each question below is based on a number series.

      Identify the pattern and answer accordingly. A sequence {Tₙ} is defined as: T₁ = a, T₂ = b and for n ≥ 3, Tₙ = Tₙ₋₁ + Tₙ₋₂ If T₅ = 43 and T₆ = 69, what is the value of (a + b)?
      A 11 Correct Answer Incorrect Answer
      B 17 Correct Answer Incorrect Answer
      C 21 Correct Answer Incorrect Answer
      D 13 Correct Answer Incorrect Answer
      E None of these Correct Answer Incorrect Answer

      Solution

      ATQ, Compute T₃, T₄, T₅, T₆ in terms of a and b. T₁ = a T₂ = b T₃ = T₂ + T₁ = a + b T₄ = T₃ + T₂ = (a + b) + b = a + 2b T₅ = T₄ + T₃ = (a + 2b) + (a + b) = 2a + 3b T₆ = T₅ + T₄ = (2a + 3b) + (a + 2b) = 3a + 5b Given: 2a + 3b = 43 …(i) 3a + 5b = 69 …(ii) Multiply (i) by 3: 6a + 9b = 129 Multiply (ii) by 2: 6a + 10b = 138 Subtract: (6a + 10b) − (6a + 9b) = 138 − 129 b = 9 From (i): 2a + 3×9 = 43 2a + 27 = 43 → 2a = 16 → a = 8 Thus, a + b = 8 + 9 = 17.

      Practice Next
      ask-question