Transcript How To Round

ESTIMATION
Estimating
Guess how many?
There are 20 pens
Estimating
Guess how many?
There are 15 kites
Estimating
Guess how many?
There are 25 pencils
Estimate the number of
bricks used to build this
portion of a chimney.
You´re answers vary because you are
estimating.
It is when you make a guess of what you think
the answer might be close to, such as when you
estimate how many bricks were used to build
the chimney.
ROUNDING
Rounding two-digit numbers
RULES FOR ROUNDING
Two-digit number will be
1.
rounded to the nearest
ten.
Underline the number in the place
value you will round.
2.
26
Look at the number to the right of the
underlined number.
3.
30
If the number to the right is 0, 1,
2, 3, or 4, then the underlined
number stays the same.
4.
So we can say that th
closer to 30 than to 20.
5.
If the number to the right is 5, 6, 7,
8, or 9, then the underlined number
needs to go up one more number.
Every number to the right of the
underlined number becomes a zero.
Rounding three-digit numbers
RULES FOR ROUNDING
Three-digit number
1. Underline the number in the
will be rounded to
place value you will round.
the nearest
2. Look at the number to the right
hundred.
of the underlined number.
3.
520
500
So we can say that the
number 520 is closer to
500 than to 600.
If the number to the right is 0, 1,
2, 3, or 4, then the underlined
number stays the same.
4.
5.
If the number to the right is 5, 6,
7, 8, or 9, then the underlined
number needs to go up one more
number.
Every number to the right of the
underlined number becomes a zero.
26 is closer to 30 than to 20.
26
20
30
520 is closer to 500 than to 600.
50
0
520
600
Estimating sums
First, round all the numbers using the RULES
FOR ROUNDING .Then, perform the
operations.
12
+ 8
-------
10
+ 10
------20
Estimating differences
First, round all the numbers using the RULES
FOR
ROUNDING. Then, perform the operations.
-
250
- 110
------
300
- 100
------200
Now you practice.
25
78
36
158
689
324
Round these numbers.
30
80
40
200
700
300
Rounding Whole Numbers
Through Millions
By Mr. Bales
Objective
» You will be able to round whole numbers
through the millions to the nearest 10, 100,
1,000, 10,000, or 100,000
Problem
» Each year immigrants from around the
world come to the United States. In
2003, California schools welcomed
175,090 immigrant students.
» What is 175,090 rounded to the nearest
thousand?
How To Round
» Let’s look at this number 175,090.
» First, underline the place value that you want to
round.
» Then, look at the digit to the right. If the digit is 4
or less, the digit in the rounding place stays the
same.
» If the digit to the right is 5 or more. The digit in
the rounding place increases by one.
» Last, change all the digits to the right of the
rounding place to zero.
Game Time!!
» Round to the nearest
hundred
» 71,105
» 654,354
» 678,947
» Round to the nearest
ten thousand
» 1,256,876
» 23,786,983
» Round to the nearest
hundred thousand
» 234,654,899
» 3,853,216
» Round the nearest
billion
» 6.834,652,985
» 87.476,634,321
Your turn!
Your turn!
Estimate each product, addition
and subtraction.
1. 62 X 82
2. 59 X 48
3. 74 X 302
4.324587-52418
5. 4681+9284
6. 31,877 – 12,794
7. 11,284,788 + 835,785,022