This Application Problem is a part of the Lesson 17, Unit 2, Grade 3. Upon evaluating the usefulness of rounding to the nearest ten or hundred, invite students to propose a better method of rounding to check the reasonableness of answers. In this example, rounding one addend to the nearest hundred is a useful strategy. The doctor prescribed 175 milliliters of medicine on Monday and 256 milliliters of medicine on Tuesday. Estimate how much medicine he prescribed in both days.