Future value calculator. FV=PV * ((1+r)^t), FV = future value, PV = present value, r = interest rate, t = compound time

fv.js

const fv = (pv, r, t) => {
  // FV = PV * ((1+r)^t)
  return pv * Math.pow(1 + r, t);
}

const interest = (pv, fv, t) => {
  // r = sqrt[t](FV / PV) - 1
  return Math.pow(fv / pv, 1/t) - 1;
};

// What is the future value of $1,000 at an interest rate of 11% for 5 years?
console.log(fv(1000, 0.11, 5).toFixed(2));
console.log(fv(1000, 0.02, 5).toFixed(2));

// What is the interest rate after 5 years for a future value of $1,685.06 from a present value of $1,000?
console.log((interest(1000, 1685.06, 5) * 100).toFixed(2) + '%');
console.log((interest(1000, 1104.08, 5) * 100).toFixed(2) + '%');

output.txt

1685.06
1104.08
11.00%
2.00%