When working in real terms, ensure all cash flows are valued in terms of today's money and convert the nominal discount rate to real terms using the formula: rr = (1 + rn) / (1 + i) - 1
When working in nominal terms, all cash flows must be in nominal terms. If a cash flow is in real terms, convert it to nominal terms using: Cnominal = (1 + i)^s * Creal