2. Rounding means reducing the digits in a number while trying
to keep its value similar. The result is less accurate, but
easier to use.
There are 3 ways we can round numbers:
Using a number line:
Using place value
Using mental math
ROUNDING
3. Using a number line can be an easy method to round
numbers, but you need to be very careful and place the
numbers correctly.
Example: I want to round the number 134,456 to the nearest
hundred thousand. In order to do that I must first know where
the hundred thousand digit is. In this case, because I already
know place value, I know that the hundred thousand place is
the 1.
USING A NUMBER LINE
1 3 4 4 5 6
Hundred
thousands
Ten
thousands
Thousands Hundreds Tens Ones
4. I make a number line and place my number 134,456 between
100,000 and 200,000 thousand.
I can see that my number is closer to 100,000 than to
200,000 so:
134,456 rounded to the nearest hundred thousand = 100,000
USING A NUMBER LINE
134,456
5. Number lines can take a lot of time, especially if you need to
do a lot of exercises. A sometimes quicker way is using place
value.
Using this method, you need to follow a couple of steps.
Before following them, though, you need to remember place
value in order to know the digit you are going to be rounding.
In this case, we want to round 134,456 to the nearest
hundred thousand, so we have to determine which digit is in
the hundred thousands place.
USING PLACE VALUE
1 3 4 4 5 6
Hundred
thousands
Ten
thousands
Thousands Hundreds Tens Ones
6. Step One:
Look to the number of the right.
134,456 Since we are going to round the 1, we need to look at the
number on the right of it, which is the 3.
Step Two:
If it’s a number between 0-4, the rounding number stays the same.
If it’s a number between 5-9, add 1 to the rounding number.
3 is between 0-4, therefore, the rounding number (1) stays the same.
Step Three:
Replace the remaining numbers to the right of the rounding number with
zero.
100,000
USING PLACE VALUE
7. This is perhaps the easiest way to round, but you must be very
careful when employing this method.
We follow the first few steps of the other methods:
Determine which digit we need to round.
Look to the digit on the right.
We are rounding 134,456 to the nearest hundred thousand. We
need to round the 1, and we look to the 3 for guidance.
If we use mental math, we know that the number 13 (we took the
two digits and made them a number) is closer to 10 than it is to
20, therefore, the first two digits remain as 10, and we simply
replace the other digits with zero.
134,456 to the nearest hundred thousand = 100,000.
USING MENTAL MATH
8. 548,652 to the nearest TEN THOUSAND.
Number line:
Place Value:
Look to the right of the ten thousands place.
8 is between 5-9 so I add 1 to my rounding number (4+1 = 5).
Turn the remaining numbers to zero.
550,000
Mental Math:
Look to the right of the ten thousands place.
48 is closer to 50 than to 40, so I replace those two digits with 50.
Turn the remaining numbers to the right to zero.
550,00
MORE EXAMPLES
5 4 8 6 5 2
Hth Tth Th H T O
548,652
9. Practice these exercises in your notebook, then look at the
Answer Key to see if you got it right! You may use the method
that is easiest for you.
(1) 69,587 to the nearest HUNDRED
(2) 709,051 to the nearest HUNDRED THOUSAND
(3) 1,405 to the nearest TEN
(4) 33,985 to the nearest THOUSAND
(5) 95,201 to the nearest TEN THOUSAND
PRACTICE!
10. These are the answers to the previous slide’s exercises.
(1) 69,600
(2) 700,000
(3) 1,410
(4) 34,000
(5) 100,000
ANSWER KEY
11. Lesson prepared by: Mrs. Shiara Agosto
For: 4th grade class, C.E.T. Colegio Myrang, Carolina, Puerto Rico
Common Core Standards: CC.4.NBT.3 Use place value
understanding to round multi-digit whole numbers to any place.
DISCLAIMER: You may distribute, copy, and/or alter the
contents of this lesson for personal or classroom use, as long
as you leave this slide intact and give credit where credit is due.
Thank you.
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