- Third Grade
- 55 minutes
- Standards: 3.NBT.A.1
Help your students understand rounding without rhymes or tricks. Students will use an open number line to round and then take part in a fun game that will get them moving around the room.
Students will be able to round to the nearest ten using an open number line.
Introduction (5 minutes)
- Let students know that they will be learning how to round to the nearest 10 today.
- Let students know we round when we do not need an exact answer. Rounding makes numbers simpler, but keeps it's value close to the original number.
- Discuss times in life when we will need to round, such as grocery shopping or when we tell people our age.
Explicit Instruction/Teacher Modeling (10 minutes)
- On the board, draw an open number line.
- Write "42" on the board.
- Ask students to determine with their group which two 10s 42 is between. Students should determine 42 is between 40 and 50.
- On the board, draw 3 hash marks. The first hash mark should be close to the arrow on the left of the number line, the second hash mark should be in the very middle of the number line, and the third hash mark should be near the right arrow of the number line.
- Under the first hash mark, label it as 40.
- Under the third hash mark, label it as 50.
- Ask students to determine what number comes halfway between 40 and 50. Students should respond that this number is 45.
- Label the middle hash mark as 45.
- Ask students to look at the number line you have created and determine where 42 would come on the number line.
- Plot 42 on the number line.
- Show students that 42 is closer to 40 than it is to 50, therefore 42 would round to 40 when rounding to the nearest 10.
- Use the same strategy as listed above and model rounding 87 to the nearest 10.
- Use the same strategy as above and list the number 35 on the board.
- Ask students what they notice about 35. They should reply that it is exactly halfway between 30 and 40.
- Let students know that when there is a number exactly halfway between two tens, we always round up, so 35 would round to 40.
Guided Practice/Interactive Modeling (10 minutes)
- Ask students to take out their dry erase boards.
- Ask students to draw an open number line and round 76 to the nearest 10.
- Circulate to check for understanding and correct representation of the open number line.
- As students correctly show their open number line, have them show how to round 24, and then 55, to the nearest 10.
Independent Working Time (20 minutes)
- As students gain understanding, introduce the rounding around the room activity.
- Split students into 5 groups. Give each group a plastic bag of numbers.
- Explain to students that they will take turns drawing a number out of the bag. They will then tell their group their number and what 10 it rounds to. If the group agrees, that students will go place the number under the correct "10" around the room. If the group does not agree, or the student needs to, they may draw an open number line to determine which 10 their number rounds to.
- Students will take turns until all the numbers in their bag have been used.
- After all numbers have been place under the 10s go to the first set at 0 and say all the numbers that were placed there. Ask students to give a thumbs up if they agree or a thumbs down if they do not. For any numbers that are not with the correct rounded number, ask a student volunteer to move it to the correct location.
- Continue this quick check for all numbers.
- Enrichment: Students who are advanced and finish early may get one of the plastic bags and practice rounding individually. These students can also complete the Rounding to the Nearest Ten worksheet.
- Support: Assemble a small group of any struggling learners that are having trouble after the individual assessment. Work together to draw number lines. Explicitly point out the proximity from the plotted number to the ten it is closest to.
Assessment (5 minutes)
- Ask students to take out a piece of paper and a pencil.
- On the board write the numbers 88, 16, and 65.
- Ask students to draw 3 open number lines on their paper. Let the students know each open number line should have the two tens the number is between, the halfway point, and their number plotted and labeled on the number line.
- As students turn in their number lines, quickly review for accuracy and reteach with any students if necessary.
Review and Closing (5 minutes)
- Ask students to discuss with their group situations in their life when they may find rounding useful.
- Post a list of ideas on the board.