Every year your money is in the bank, interest is adding onto it, so it is important to start saving early. Betty saved $150 for 40 years with APR 3% and ended up with $138,909. Merriweather waits 20 years before she starts saving, and she only saves for 20 years. However, because of her late start, Merriweather thinks saving twice as much as Betty each month will give her an equal balance. But as you will discover, having money in the bank for fewer years will earn less interest. 13. How much will Merriweathers 401(k) have in it when she retires after only 20 years of saving $300/month?