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Q&A #7392

Teachers' Lounge Discussion: How do I teach rounding to fourth graders who just don't seem to get it?

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From: Loyd <Loydlin@aol.com>
To: Teacher2Teacher Public Discussion
Date: 2004092605:16:21
Subject: Re: rounding to the nearest ten thousand

On 2004092515:39:50, Carmen Camacho wrote:
>my grandson si learning to round to the nearest ten thousand and he
>has the numbers 999,533 to be rounded. please help him how to rounded
>to the nearest ten thousand
>thak you 
>

This problem has carries, so I will show you two or three ways to
think about it:

First, make sure your grandson can say the names of the place names
starting at the far right:

Ones, tens, hundreds, thousands, ten thousands etc.  

So, the place of interest is the 5 digits from the right which is the
middle 9 in your problem.

999,533. Place your pencil on that digit and look at the one to the
right which is also a nine.  If the digit to the right is 5 or
greater, add one to the ten thousand place and change all the digits
to the right to zeros.  That makes your answer 1,000,000.

It might be easier to think this way:  Inspect the digit to the right
of the ten thousand place which is the thousand place.  If the
thousand place is 5 0r greater add 1 to the ten thousand place. Then
all the digits to the right become zero.

 999,533
 +1
---------
1,000,000  What we really have is 100 ten thousands vice 99 ten
thousands.  Which leads to another way to think about it:

99,9533  Use the comma to set off how many ten thousands there are
vice thousands.
Ask the question: Is 99,9533 closer to 99 ten thousands or is it
closer to 100 ten thousands?  It is closer to 100 ten thousands, so
that is the answer which equals 1,000,000. 

If the problem had been, 999,433 the answer would have been
ninety-nine ten thousands=990,000.

Here is a last resort way to do it.  Just add a 5 to the digit to the
right of the place of interest. 
999,533
 +5
---------
1004533  change digits to right of ten thousand place to zero.

I will round a bunch of problems using the last method:

Round 158 to the nearest 100
158
+5  ---> add 5 to tens place
---
208 change last 2 digis to zero-->200

Round 148 to the nearest 100
148
+5---> add 5 to tens place
---
198 change last digit to zero-->100

Round 3587 to the nearest thousand
3585
+5---> add 5 to hundreds place
----
4085  change all digits to right of thousand to zero
4000 is the answer. 
Round 888888 to the nearest 1000
888888
  +5---> add 5 to hundreds place
-------
889388 --->889000
 
Someone may have a simpler way to explain it.   

Another way to do it is get a book with answers, and practice,
practice, practice.  It will soon become 2nd nature.  

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