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IAI Actuarial Core Principles · Actuarial Mathematics for Modelling · Project appraisal

For a project the net present value is +₹4,000 at 10% per annum and -₹1,000 at 15% per annum. Using linear interpolation between these two rates, what is the estimated IRR?

The interpolated IRR is 14.00%. NPV falls from +4,000 to -1,000 across 5 percentage points, so it hits zero 4/5 of the way along: 10% + 5% × 4,000/5,000 = 14%. Using the midpoint or reversing the weights gives wrong values.

  1. A12.50%
  2. B11.00%
  3. C13.00%
  4. D14.00%Correct
  5. 16.00%

Explanation

Interpolating: IRR = 10 + 5 × 4,000/(4,000 + 1,000) = 10 + 4 = 14.00%. The 12.50% option takes the midpoint, ignoring that NPV is much closer to zero at 15%. The 11.00% option reverses the weights (10 + 5 × 1/5).

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