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Checking a reported project IRR ranking

A ranking story fails if the claimed IRR does not make its own schedule’s NPV zero.

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Write the two synthetic schedules

Original exercise schedules
ProjectCF0CF1CF2
A−100,00060,00060,000
B−100,00010,000120,000

Solve the two quadratic checks

Let a = 1 + r. A satisfies a² − 0.6a − 0.6 = 0, giving IRR 13.066239%. B satisfies a² − 0.1a − 1.2 = 0, giving IRR 14.658561%.

Compare correctly computed values

At 10%, A has NPV 4,132.231405 and B 8,264.46281. B also has the higher correctly calculated IRR. These schedules therefore do not demonstrate a conflict between the two rankings.

Use a substitution check as a quality control

A reported rate of 12.7% for B is not its root. Recalculate the NPV at a reported rate before relying on a narrative about timing or ranking. This exercise is an arithmetic audit, not an investment recommendation.

Further references