Rate(n1, n2, n3)
0.0844717712 (or 8.45%), which is the interest rate per period needed for an $8000 present value to grow to $12,000 in five periods.
0.04427378243 (or 4.43%), which is the interest rate per month needed for the present value to grow to $10,000 in four years.
This example uses variables in place of actual numeric values or expressions.

Rate