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"In the Neighborhood"

> I teach third grade, and we will soon be ready to start
> rounding to the nearest 10 and 100. Does anyone have any
> fun activities or games to use with rounding? I'd
> appreciate any suggestions.
> Carol

To introduce rounding to my lower kids, I do a little activity called "In the Neighborhood." I explain that there is a family of grown-ups living in a neighborhood. (Draw a number line with 10 houses in a row and a "fence" in between each house). The families' names are 0, 10, 20, 30... One day a rolly polly round kid named "21" walks into the neighborhood. She wants to go to the house she is closest to. Twenty-one knows she's more than 20 but less than 30, so what house should rolly polly "round" to? I laminate a rolly polly round kid and let the students use the wipe off marker to write the new numbers as we go. We have magnetic chalkboards so I also put a magnet on the back for easy mobility. It's a great lesson for kids who cannot yet conceptualize rounding without a hands-on activity. Once they get this under their belts, estimating using rounding is a cinch. :)

P.S. A follow up is a fast paced rounding game. I made a large chart with all of the tens numbers. Each team has a rolly polly round kid. I give a number and the first player from each team has to stick the rolly polly round kid in the correct house...

Jen/3/OH, on primary elementary board

rounding tricks and sayings

In my third grade classroom we chant the army song tune---

1,2 round down 3,4 round down---1234 round down---

5,6 round up 7,8 round up 5678 round up and 9 also.

Pam Howell, on math board

rounding rhyme

I have a rhyme for you that worked well with 4/5 SLD students - we also circle and underline the numbers to distinguish - I tried this with general ed third graders also and it worked well.

1 through 4 stay on the floor
5 through 9 climb the vine

Susan Smith, in a message to Math Cats top

How can I make ROUNDING more comprehensible???

> HELP!!! I am tutoring a third grader who is struggling with
> rounding numbers to the tens, hundreds, thousands, and ten
> thousands place. How can I make the concept of rounding
> less abstract and more concrete for her? Is there a "real
> world" way to explain this concept that she might connect to?
> Mary

Use Base Ten Materials

Use base 10 materials and count out 142, for example. Tell them to round to the nearest 10. You could show this by showing that to get to 40 is only 2 cubes away but 50 is 8 cubes away, therefore 42 is closer to 40 than 50. If you do this several times with different numbers and base 10 materials, she will see why 5 is the cutoff point.

Kathy, on math board

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Ask: What are their rounding choices?

I would ask the student which two tens, hundreds, etc. the number being rounded is between. For instance, 737 is between 730 and 740 but is closer to 740. It is between 700 and 800, but is closer to 700. I am sure you have had students round 737 to 40 when asked to round to the nearest ten. I think the issue with kids and rounding is figuring out what their rounding choices are. When rounding there are only two options; once that is decided it is easy to pick which number is closer. Try this way before giving the 5 rule. This way also transfers well to rounding decimals later.

Blinda, on math board

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Use manipulatives and a code

In fourth grade we also use math manipulatives to show our students when to round up or down.

We also teach them to underline the digit that they want to round and put a dot below the digit to the right of the underlined digit.

If the number that has a dot under it is less than 5 you round down to the nearest tens, hunderds, or thousands. If the number that has a dot under it is 5 or more than you round up to the nearest tens, hundreds, ot thousands.

This number can be rounded up to 460 because the digit 6 is 5 or a greater number.

Ron Feldt, on math board

Use a code

I have my students circle the number in the place they are rounding to, then underline the digit to the right. If the underlined digit is 5 or more, the circled number is increased by one. If the underlined number is less than 5, the circled number stays the same. All the numbers to the left of the circled number stay the same; the numbers to the right become zero.

Anne, 11/15/00 on upper elementary board

"Bully" numbers kick their neighbors

I teach 3rd grade GT. I found that teaching "bully" numbers really works. For example - round 4,576 to the nearest 10,  100, or 1,000.

To the nearest 10 - What's the "bully" number. answer: 6
If the "bully" number is 5, 6, 7, 8, or 9, then the bully "kicks" its neighbor up "one" number. If the "bully" is 1,2,3,or 4, then the neighbor gets to remain the same.

The same procedure is used for 100 and 1,000.

Also, I teach the students that when rounding to nearest 10, there will be one zero (0) at the end,
for 100's, two (0's),
for 1,000, three (0's).

Rachel/Tx., on math board

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an objection to the idea of "bully" numbers

I must take exception to the teacher who wrote saying she uses the example of a "bully" who is kicking other numbers. We work so hard to have zero tolerance toward bullying at school, I hate to see it used casually in the course of teaching a math lesson!

Brenda L. Gunn, grade 4 teacher, Edmonton, Canada
in a message to Math Cats

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adapting "bully" numbers to a more positive image

The "bully numbers" posting was included in this idea bank because it addresses rounding to 10's, 100's, and 1,000's, but I agree that there must be a better analogy than "bullies." Maybe we could adapt this idea to "helpers" instead of "bullies." If the "helper" number is 5, 6, 7, 8, or 9, then the helper gives its neighbor a boost up to the next number, while the helper (and all numbers to its right) become 0. If the helper number is 1, 2, 3, or 4, then the neighbor remains the same while the helper and all numbers to its right become 0. In either case, the helper could be considered "selfless" and certainly self-effacing, as it always becomes 0. This is not the behavior of a bully!

Wendy of Math Cats

Use a number line

I used a number line so they could see which number the number to be rounded was closer to. This helped them see it visually. It worked for many who were not understanding why we round up for 5 and greater and down for less than 5.

mine did too, on upper elementary board

Drive up a mountain

I draw a mountain on the board. I put a 0 at the left and right base of the mountain and 5 at the top of the mountain. I then write the numbers 1 - 4 up the left side of the mountain and 6 - 9 on the right side of the mountain.

I have a white board and can use magnets so I cut a car out of a large magnet and begin my trip up the mountain. If the number ends in 1 - 4, I drive the car to that number, get out to look at the view and forget to put the car in park. The first time that I do this activity, I ask what happens to the car if it's not in park and the students tell me it will roll. We discuss whether it will roll up the hill to the next number or back down to the lower number. We talk about the fact that a car won't roll up so the number rounds to the lower number.

If the number ends in 6 - 9, we repeat the process with the car, discuss whether it will roll forward or backward when I look at the view, and round to the higher number. If the number is 5, we determine that the engine end of the car probably weighs more than the empty trunk, so the car will roll forward to the higher number.

This has worked well with at-risk students in summer school and with various levels of math students during the year. Sometimes, I'll give them a piece of construction paper with a mountain and a small toy car so they can work problems at their desk.

Lynn Tessin, in a message to Math Cats

a numberline shaped like a hill

Your site is great. I use a number line to teach rounding. We learn about midpoint first, and I explain about the five or greater rule. I draw the number line in the shape of a hill, and tell the kids it's like someone is pulling the string up at the midpoint. If they were 62, for example, which way would they slide? (Down to the left towards 60!) It's similar to the "car on the mountain" idea, and it really works!

Brenda L. Gunn, grade 4 teacher, Edmonton, Canada
in a message to Math Cats

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