Round ‘Em Up!
Students will be able to round whole numbers to the nearest ten or hundred.
Introduction (5 minutes)
- Call students together.
- Give students the following scenario: They're at the store and need to buy something that costs $28, but they only have ten dollar bills. Ask them how many hundred dollar bills they would need to give the person at the cash register. (A student should be able to say they would need three ten dollar bills.)
- Congratulate students on the fact that they have just rounded the number 28 to the nearest ten (30). Explain that rounding a number is a way to make it more convenient for calculations.
- Ask students if they can think of any other times when they might need to round a number. (Almost any time you would need an estimate, it is appropriate to round.)
Explicit Instruction/Teacher Modeling (10 minutes)
- As a whole group, have students think up a number that is at least 6 digits long, e.g. 57,853. Write the number in a place where everyone can see it.
- Looking at the number, have students review place value. Above each number, label the different place values. (3 is in the ones, 5 is in the tens, 8 is in the hundreds, 7 is in the thousands, and 5 is in the ten thousands)
- Tell the students that they are going to practice rounding the number to the hundreds place. The first step is identifying the number in that position.
- Once students have identified that the number 8 is in the hundreds place, model drawing a line under that number with an arrow pointing to the number on the right side of the 8.
- Explain to students that everything to the left of the line will stay the same. (The numbers are 5 and 7 in this case.)
- To determine whether the number 8 stays the same, students should follow the arrow and look to the number right beside the eight. If this number is 5 or greater, 8 rounds up to 9. If the number is less than 5, 8 stays the same. In this, case the number is 5, so the 8 rounds up.
- Once students have determined that the number 8 rounds up, inform them that all of the numbers to the right of the number with the line become zeros. Thus 57,853 rounded to the nearest hundred is 57,900.
- Have students come up with another number and practice again as a whole group. Go through the same process of drawing a line with an arrow pointing to the number on the right.
- For an added challenge, choose another place value to round to, like the tens or thousands place.
Guided Practice/Interactive Modeling (10 minutes)
- Once students seem to understand the process, allow some students to become the teacher and take turns leading the class through the steps of rounding numbers to different place values. (Students might come up with long, complicated numbers for their classmates to round, so it may be important to put a limit on the length of the number.)
- After a few rounds of student teachers, break the class up into pairs or small groups. Give each student a piece of paper and explain to them that they should write down 20 numbers (at least 6 digits long) for their partner to round. After students have done this, they should trade papers.
- Call out different place values for students to round the first few numbers to. For example, round number one to the hundreds place, round number two to the tens place, etc.
- As students are rounding, walk around and observe to make sure that everyone is on the right path. Correct any misconceptions and remind students not to skip any steps.
- When it seems like students are on the right path, instruct everyone to round each of the 20 numbers to the ten thousands, thousands, hundreds, and tens place. Ask if there are any final questions before sending them off to work independently.
Independent Working Time (15 minutes)
- While students are working, adults should be circulating, answering questions, and providing assistance. It can be helpful to leave the examples the class did together visible in a prominent location. If students finish early, have them check over their neighbors' work.
- Enrichment: For students who need a greater challenge, rounding when a decimal is involved can increase the difficulty.
- Support: For students who need extra assistance, working with partners can help scaffold the activity. Additionally, providing place value charts can help students find the place values to round. Writing out the steps for students and leaving this in a visible location as they work can also help students to remember what they need to do.
Assessment (10 minutes)
- Whether or not the objective has been met can be determined based on participation in class discussions and how successful students are at rounding during their individual work time.
- For an additional assessment tool, students can be given a list of numbers and place values to round to for homework.
Review and Closing (5 minutes)
- Call students together as a group.
- Ask them to share their experiences with rounding. (Is there any part of the process that is still particularly tricky or challenging? Were any numbers or place values extra hard to round? Once they got comfortable with the process, did students start making silly mistakes? If so, how can they avoid this in the future?)
- Remind students of the rounding steps. (First, determine which number is in the place value being rounded to. Draw a line under this number with an arrow pointing to the right. Look at the number directly to the right of the number that has a line under it. If it is 5 or greater, the number with the line goes up by one and every number to the right becomes a zero. If the number to the right of the number that has a line under it is less than 5, the number with the line stays the same and every number to the right becomes zero.)
- If students need some more practice, the class can do a few more examples as a whole group.
- Remind students that they need to be careful to find the number in the right place value. Also, stress that 5 is the magic rounding number that makes numbers go up.