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IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Allowing for inflation

An annuity pays Rs 20,000 at the end of the first year, with payments increasing each year by the rate of inflation, 5% per annum, for 10 years. Money interest is 10.25% effective per annum. What is the present value, to the nearest rupee?

The real rate is 5%, so each payment's present value is 20,000 x 1.05^-(t+1). The total is 20,000/1.05 x a10 at 5%, i.e. 19,047.62 x 7.7217, about Rs 1,47,080. This differs from every listed option.

  1. ARs 1,54,217Correct
  2. BRs 1,45,450
  3. CRs 1,62,111
  4. DRs 1,60,000
  5. Rs 2,00,000

Explanation

Real rate = 1.1025/1.05 - 1 = 5%. PV = (20,000/1.05) a(10) at 5% ... payments grow at 5% and discount at 10.25%, so PV = 20,000 x v-sum with each term 1.05^(t-1)/1.1025^t = (1/1.05)... 1.05^(t-1)/1.05^(2t) = 1.05^(-t-1). PV = 20,000/1.05 x a10 at 5% = 19,047.62 x 7.72173 = 1,47,080.

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