To begin this part of the lesson, ask:
- What is 3639 rounded to the nearest thousand? (4000) How did you decide? (Possible response: 3689 is between 3000 and 4000. It is more than 600 away from 3000 and just a little more than 300 away from 4000. Since it is closer to 4000, I rounded to 4000.)
- What is 3639 rounded to the nearest hundred? (3600) How did you decide? (Possible response: 3639 is between 3600 and 3700, but it is closer to 3600.)
- How do you round 3639 to the nearest ten? (Possible response: When you look at 3639, it is between 3630 and 3640. 39 is much closer to 40, so you round it to 3640.)
Direct students to the Rounding Decimals section of the Student Guide and ask them to work with a partner and use the decimal grid that is shaded to show 0.892 to complete Questions 10–12. In each of these questions, students use the location of 0.892 on a number line to make decisions about how to round 0.892. In Question 10, students are asked to round 0.892 to the nearest hundredths. They first locate 0.892 on a number line that has 0.89 and 0.90 as the endpoints.
- This number line is divided into ten equal sections. What is the value between each large mark on this number line? (Each step is equal to one-thousandth.)
- Count each step on the number line starting with eighty-nine hundredths. (.89, .891, .892, .893, .894, .895, .896, .897, .898, .899, .90)
- Look at .892 on the number line. Is it located closer to .89 or .90? (0.892 is closer to 0.89 than it is to 0.90; therefore, 0.892 rounded to the nearest hundredth is 0.89.)
In Question 11, students round 0.892 to the nearest tenth. For this question students use a number line that has 0.8 and 0.9 as endpoints since 0.892 lies between these two tenths. The number line is divided into ten equal segments.
- What is the value between each large mark on this number line? (Each step is equal to one-hundredth.)
- Count each step on the number line starting with .8. (.8, .81, .82, .83, .84, .85, .86, .87, .88, .89, .9)
- Looking at the number line, is .892 closer to .8 or .9? (.9)
- What then, is .892 rounded to the nearest tenth? (.9)
Students round 0.892 to the nearest whole number in Question 12.
- Between which two whole numbers is .892 located? (zero and one)
- When you look at the number line for Question 12, what is the value between each of the large marks on this number line? (one-tenth)
- We know that .892 is located between .8 and .9 on this number line. Is .892 closer to 0 or 1? (1)
- What is .892 rounded to the nearest whole number? (1)
After discussing Questions 10–12 in the Student Guide, have students work with a partner to complete Questions 1–11 on the Decimals: A Closer Look pages in the Student Activity Book. As students complete these questions, encourage them to share their solutions and their strategies with the class.
