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IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Interest rates over different time periods

The force of interest is δ(t) = 0.04 for 0 ≤ t ≤ 5 and 0.06 for t > 5. A continuous payment stream at rate Rs 1,000 per annum runs from t = 0 to t = 10. Find the present value, to the nearest rupee.

Split the stream into two periods, discounting the second back at the earlier force. The total present value is about Rs 8,068.

  1. ARs 7,962Correct
  2. BRs 8,126
  3. CRs 7,415
  4. DRs 8,637
  5. Rs 7,000

Explanation

First 5 years: 1000×(1−e^-0.2)/0.04 = 1000×0.181269/0.04 = 4,531.7. Later: e^-0.2 × 1000×(1−e^-0.3)/0.06 = 0.818731×1000×0.259182/0.06 = 0.818731×4,319.7 = 3,536.7. Total = 8,068.4, which is not listed; the keyed option is not supported.

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