1. Rounding

2. Rules for Rounding 350 345 Examples: 1.) Round 345 to the nearest ten.
1. Identify the place that you are
rounding to.
2. Look at the number to its right.
5 or more, raise the score.
4 or less, let it rest
3. All of the numbers to the right of the place will become zero.
Examples:
1.) Round 345 to the nearest ten.
345
350
5 is “5 or more”,
so raise the score.

3. Rules for Rounding 43.4 9 43.42 8.75 2 is “4 or less”, so let it rest.
2.) Round to the nearest tenth.
43.42
3.) Round 8.75 to the ones place.
8.75
2 is “4 or less”,
so let it rest.
43.4
7 is “5 or more”,
so raise the score. 9

4. Try These in your Notebook Directions: Use the number below to round to the given place values
45,678,
TENTHS - ________________
TEN THOUSAND- ____________________
THOUSANDTH- _____________________
TEN MILLION - _____________________
NEARST WHOLE NUMBERS - ____________
45,678,934.6
45,680,000
45,678,
50,000,000
45,678,935

5. Estimation

6. Estimation Estimation is: It is not: using easy mental strategies
Simplified
mental
calculation
Estimation is:
using easy mental strategies
using number sense
using a variety of strategies
getting close to the exact answer
It is not:
just a guess
doing hand calculations
using a calculator
exact
Quickly and easily get a number that is close enough to the exact answer to be useful

7. Try These Actual Answer: 4,552 Actual Answer: 6,597
Directions: Get a quick estimate in your head. Do the problem. Check to see if your answer is reasonable. = =
Good estimate would be 5,100
Another good estimate 4,600
Actual Answer: 4,552
Good estimate would be 6,600
Another good estimate 7,000
Actual Answer: 6,597

8. Real World Problems

9. Can I buy four for $100? 23 Explain Yes
4 x $25 = $100 and $23 is less than $25
$23 rounds to $25 and 4 x $25 = $100 (high estimate)
$23 rounds to $20 and 4 x $20 = $80 (low estimate)

10. $37 Can I buy three for $100? Explain No 3 x $40 is $120

11. $13.87 Can I buy five for $60? Explain No
5 x $15 = $75 which is more than $60.
5 x $14 = $70 which is more than $60.
$60 divided by 5 = $12, and $13.87 is more than $12.00.
The soccer ball would have to cost ______ or less for me to purchase five of them for $60.
$12.00

12. Can I buy three for $20?
CHESS
Explain
$4.95
Yes
3 x $5 = $15

13. Estimating with Compatible Numbers (When numbers are grouped together to make computations easier; estimation becomes almost entirely “mental”.)
Often used to estimate the answer to multiplication and division problems.
Compatible numbers make it much easier to estimate the answer to a problem.

14. 142 ÷ 59
Can you think of a pair of numbers, that are close to these, that can be divided mentally?
Actual Answer:
2.4 2
140 ÷ 70 =
120 ÷ 60 = 2

15. 226 ÷ 71 Actual Answer: 3.2 240 ÷ 80 = 3 210 ÷ 70 = 3 240 ÷ 60 = 4
226 ÷ 71
Can you think of a pair of numbers, that are close to these, that can be divided mentally?
Actual Answer:
3.2
240 ÷ 80 = 3
210 ÷ 70 = 3
240 ÷ 60 = 4

16. 54 x 7 Actual Answer: 378 55 x 10 = 550 50 x 10 = 500 60 x 5 = 300
Can you think of a pair of numbers, that are close to these, that can be multiplied mentally?
Actual Answer:
378
55 x 10 =
550
50 x 10 =
500
60 x 5 =
300

17. Actual Answer:
3,471
267 x 13
Can you think of a pair of numbers, that are close to these, that can be multiplied mentally?
270 x 10 =
2,700
300 x 10 =
3,000
250 x 10 =
2,500

18. Go to Compatible Numbers Power Point Presentation