Mara found the length of time of an investment. The principal of the investment was $4,300, the interest rate was 6.2 percent, and the interest was $2,666. Mara made an error in her work. I = p r t. 2666 = (4300) (0.062) t. 2666 = (266.6) t. StartFraction 266.6 over 2666 EndFraction = t. 0.1 = t.