Lesson Summary - Rate problems, including constant rate problems, always count or measure something happening per unit of time. The time is always in the denominator. - Sometimes the units of time in the denominators of the rates being compared are not the same. One must be converted to the other before calculating the unit rate of each. Who walks at a faster rate: someone who walks 60 feet in 10 seconds or someone who takes 5 seconds to walk 25 feet? Review the lesson summary before answering!