For which situation does one quantity change at a constant rate per unit interval relative to another quantity? responses for every day that passes, a person drives 54 miles. For every day that passes, a person drives 54 miles. For every month that passes, a savings account earns interest at a rate of 1. 5%. For every month that passes, a savings account earns interest at a rate of 1. 5 % %. For every week that passes, a vine doubles in length 2 times a week. For every week that passes, a vine doubles in length 2 times a week. For every year that passes, a population of insects increases by 6%.