When most parents of school-age children learned how to round numbers we were taught an answer-getting technique. The trick goes something like this:
Round 49.365 to the tenths place: If you want to round a number to the tenths place, look at the digit in the tenths place, in this case, the 3. When you find the number, look one space to the right. If the number is 5 or more, you round UP... if it is 4 or less, you round DOWN. In this case, the rounded number is 49.4 While this rounding procedure is simple, and you get the right answer every time. So what's the problem? Well, when you learn this procedure alone you don't really understand what is happening with the numbers. "Why did you round up, Beatrice?" "I rounded up because the 7 is greater than 5." Instead of teaching a simple rounding procedure now, math teachers work to help students understand the CONCEPT of rounding. We want our students to learn what is really going on with the numbers. When I ask my students to round 49.365 to the tenths place they will determine how many total tenths there are in the number. We call this DECOMPOSING the number, which they have been doing since kindergarten (if they have used the Eureka math curriculum). Students decompose 49.365 to 493 tenths 6 hundredths 5 thousandths. Since they want to find the closest tenth, they create a number line with 493 tenths or 49.3 at the bottom, and 494 tenths (one extra tenth) or 49.4 at the top. Then they determine the MIDPOINT between the two numbers, which requires them to look into the hundredths place. They determine that the midpoint is 49.35, and they place this on their number line. Next, students look to place 49.365 on the number line. If done correctly, they will place 49.365 slightly above the midpoint since the 6 in the hundredths place indicates that it is higher than the 5 in the hundredths place of 49.35. Since the number is above the midpoint, we round to the higher number because it is closer. We have determined that 49.365 is closer to 49.4 when rounded to the nearest tenth. The drawing below illustrates what this solution should LOOK like.
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This assignment is a fun way for students to get to know each other, and for Mr. Crum to get to know all of the students. Please pay careful attention to the details of the assignment, and the grading rubric. Students will receive a copy of the assignment in class. If the copy is lost, students will be responsible for making another copy with the attached document. Completed projects will be presented in call, and are due no later than Tuesday, August 15 at 8:15am. |