seegongsik
Grade 4 (age 9-10)

grade 4 Estimation — Number Range

Estimation and Number Range

Rounding replaces a big number with a nearby number that is easier to use, such as a number of tens, hundreds or thousands. The same 3746 becomes 3750 rounded to the tens place but 3700 rounded to the hundreds place, so the result depends on the place you round to, and rounding up, rounding down and rounding to the nearest give different answers too. To describe a range of numbers, at least and at most include the boundary number, while more than and less than leave it out; you see these words in age limits and price lists. Change the number and the place to see where the rounded value lands on the number line, and change the boundary to see how the four ranges are drawn.

Which Place to Round To

🔍 Which Place Do You Round To?
①Rounding 3746 to the tens place looks at the ones digit, 6, and goes up to 3750
②Rounding it to the hundreds place looks at the tens digit, 4, and goes down to 3700
③If the digit just to the right of the rounding place is 5 or more, round up; if it is less than 5, round down
④Rounding up always goes up if any lower digit is not 0, and rounding down changes all the lower digits to 0
3746
hundreds

At Least, At Most, More Than, Less Than

50
💡 Is the Boundary Included?
①At least and at most include the boundary, so it is drawn as a filled dot (●)
②More than and less than leave out the boundary, so it is drawn as an open dot (○)
③At least and more than run toward bigger numbers; at most and less than run toward smaller ones
④At least 50 includes 50, but more than 50 does not

Summary

At Least and At Most
At least 50: 50, 51, 52, …
Numbers equal to 50 or greater
More Than and Less Than
More than 50: 51, 52, 53, …
Numbers greater than 50; 50 itself is not included
A Range of Numbers
At least 30 and less than 50: 30, 31, …, 49
A range that includes 30 but not 50
🎯 Summary
①The result of rounding depends on the place you round to
②To round, look at the digit just to the right: 5 or more goes up, less than 5 goes down
③At least and at most include the boundary and use a filled dot (●)
④More than and less than leave out the boundary and use an open dot (○)
⑤Two conditions together, like at least 30 and less than 50, describe a range of numbers

Examples and Unit Test

Example 1
Round 3746 to the tens place.
1
To round to the tens place, look at the ones digit just to its right. The ones digit is 6.
2
6 is 5 or more, so round up to 3750.
▸ 3750
If the digit just to the right of the rounding place is 5 or more, round up; otherwise round down.
Example 2
Is 50 one of the numbers that are at least 50?
1
At least includes the boundary number.
2
So the numbers at least 50 are 50, 51, 52, … and 50 is one of them.
▸ Yes (at least 50 includes 50)
At least and at most include the boundary; more than and less than do not.
Unit Test
Which number is at least 30 and less than 50?
①28
②50
③45
④52
▸ ③ 45
1
At least 30 includes 30, and less than 50 leaves out 50.
2
28 is smaller than 30, and 50 and 52 are not less than 50. Only 45 is in the range.
← Previous
Order of Operations
Next →
Angles

Last updated