The purpose of this activity is for students to round given numbers to the nearest ten and the nearest hundred to see that the result can be the same for some numbers. Students think about what it means to round a number that is exactly halfway between two tens or two hundreds, and are introduced in the Activity Synthesis to the convention that these numbers are rounded up (MP3).

• Select previously identified students to share their responses.
• “Kiran and Priya are correct. There isn’t one closest multiple of 10 to 415 because it’s right in the middle of two multiples of 10. There isn’t one closest multiple of 100 to 750 because it’s right in the middle of two multiples of 100.”
• “In cases such as this, we round up. For example, since 415 is halfway between 410 and 420, we round up to 420 when rounding to the nearest ten.”
• “Since 750 is halfway between 700 and 800, we round up to 800.”
• ”In both situations, we could go the other way, but it is helpful if we all do the same thing.”

The purpose of this activity is for students to practice rounding to the nearest ten and the nearest hundred in context. Students work with numbers from a previous lesson to estimate the total number of students in a school. They learn that how a number is rounded (to the nearest ten or to the nearest hundred) can give different estimates for the same situation.

• Invite students to share their observations about the completed table, including whether it matched their predictions.
• “When we are estimating a total, rounding to the nearest ten or the nearest hundred can give us different results. If you were rounding to estimate a total, would you round to the nearest ten or the nearest hundred?” (The nearest ten because you get an estimate that’s closer to the total. The nearest hundred because multiples of 100 are easier to work with.)
• “Keep these ideas in mind as you use rounding to estimate in future lessons.”