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IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Duration, convexity and immunisation

A 3-year annuity-certain pays Rs 100 at the end of each year. Using an effective annual interest rate of 10%, what is the discounted mean term of its payments?

The discounted mean term is 1.94 years. The present values of the three payments at 10% are 90.91, 82.64 and 75.13; weighting the times 1, 2 and 3 by these and dividing by the total of 248.69 gives about 1.94, below the undiscounted average of 2.

  1. A1.80 years
  2. B1.94 yearsCorrect
  3. C2.00 years
  4. D2.13 years
  5. 1.76 years

Explanation

PVs: 90.909, 82.645, 75.131; total 248.685. Time-weighted sum = 90.909 + 165.289 + 225.394 = 481.592. DMT = 481.592/248.685 = 1.94. The 2.00 option is the simple average of payment times, ignoring discounting.

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