Whole Number Estimation

1
Whole Number Estimation

• Lesson 1.2
• Standards 6.C.3a, 6.C.3b

2
Use rounding

• When the question asks you
• to estimate.
• When the question asks
• about how many?
• When an exact answer isnt
• possible.
• When an answer is difficult to obtain.

3
Memorize this Poem
Find your number. Look right next door. 4 or less
just ignore. 5 or more, add 1 more.
4
Reviewing Place Value
3 , 6 7 3 , 8 9 0
Tens
Ones
Millions
Hundreds
One-thousands
Ten thousands
Hundred thousands
5
Round this number to the nearestten thousand.
Find your number.
3 6 8,9 7 1
Circle the number in the ten thousands place.
6
Round this number to the nearestten thousand.
Look right next door.
3 6 8,9 7 1
Draw an arrow to the right of the number.
7
Round this number to the nearestten thousand.
4 or less, just ignore.
3 6 8,9 7 1
8 is larger than 4 so go to the next line of the
poem.
8
Round this number to the nearestten thousand.
5 or more, add 1 more.
1
3 6 8,9 7 1
Add 1 to the 6.
9
Round this number to the nearestten thousand.
5 or more, add 1 more.
3 7 0,0 0 0
Add 1 to the 6 and all the numbers to the right
of the 7 become 0s.
10
The Answer
368,971 rounded to the nearest ten thousand is
3 7 0,0 0 0
11
Round this number to the nearestthousand.
Find your number.
3 5, 3 2 7
Circle the number in the thousands place.
12
Round this number to the nearestthousand.
Look right next door.
3 5, 3 2 7
Draw an arrow to the right of the number.
13
Round this number to the nearestthousand.
4 or less, just ignore.
3 5, 3 2 7
Since 3 is less than 4 we do not change the 5.
14
Round this number to the nearestthousand.
4 or less, just ignore.
3 5, 0 0 0
Change the numbers to the right of 5 to 0s.
15
The Answer
35,327 rounded to the nearest thousand is
3 5, 0 0 0
16
Estimating Sums and Differences
You should have added 1 to the hundreds place
because 8 is 5 or greater.
180 914
200
900
You should have kept 9 the same because 1 is less
than 4. Now add.
1100
623 59
600
You should have kept 6 the same because 2 is less
than 5.
60
You should have added 1 to the tens place because
9 is 5 or greater. Now add.
660
17
Estimating sums and differences continued
208 -114
200
Round to the nearest hundred, then subtract.
100
100
91 - 49
90
Round to the nearest tens, then subtract.
50
40
18
Estimating Products and Quotients
Since the 2 is less than 5, the 1 stays the same.
12 X 79
12 x 79
10
Rewrite problem vertically.
80
The 7 becomes an 8, since the 9 is 5 or greater.
Now multiply.
800
193 x 4
Because 9 is 5 or greater, the 1 becomes a 2.
193 x 4
200
Rewrite problem vertically.
4
When multiplying or dividing by a single digit,
keep the number the same. Now multiply.
800
19
Estimating Products and Quotients Continued..
8

469 59
60)
480
Rewrite the problem so that the two numbers are
compatible. Compatible means numbers that will
make the calculation easier.
Since I know 6 can go into 48, these 2 numbers
are considered compatible.
972 4
250
4)
1000
Again, rewrite the problem, so the numbers are
compatible.
20
Your Turn
Try these examples.
78 233
618 - 89
123 x 41
2912 52
233 78
60
618 - 89
123 x 41
200
600
100
50)
3000
80
-90
x 40
4000
280
510