Find the amount of interest Interest amount = (176400 - 112000) dollars = 64400 dollarsAs per the formula of simple interest we know thatInterest = Principal * Rate of interest * Time Rate of Interest = (Principal * Time)/Interest amount = (112000 * 30)/64400 = 3360000/64400 = 52.17So the rate of interest on the loan for the period of 30 years was 52.17%