If you save $200 per month for 20 years at 3% interest you would have?
How much interest did you earn?
Use this formula to find the Future Value of the investment:
FV=P{[1 + R]^N - 1/ R}
FV=200 x {[1 + 0.03/12]^(20*12) - 1 / 0.03/12}
FV=200 x 328.301998.......
FV =$65,660.40 - This is what your $200 per month will be worth in 20 years or 240 months.
$200 x 240 =$48,000 - This is how much you deposited in 20 years.
$65,660.40 - $48,000 =$17,660.40 - This is the interest you would earn in 20 years.