Kindergarten - Estimation

 
     
 
     
 
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K
Numbers
Estimation
Students use estimation strategies in computation and problem solving that involve numbers that use ones and tens place.
Be able to recognize the ones place and the tens place. Know the difference between a digit and a number. Know when to round a number up and when to round a number down. Understand when an estimation is reasonable and when it is not.
 

Sample Problems

(1)

Round the number 11 to the nearest tens place. What is the new number?

(2)

Add the numbers 15 and 13 together. What do you get?

(3)

Now round both numbers to the nearest tens place. Now add them together. What do you get? Is this close to the real answer?

(4)

In the number 15, which digit is in the tens place?

Learning Tips

(1)

Review number values from 0 to 100. Point out that values increase as numbers get bigger. Also point out that values decrease when we travel backward on the number line. Ex. 23 is les than 24. 24 is greater than 23.

Also practice counting by tens. Point out that the number in the tens place changes as the numbers go higher or lower.

(2)

To distinguish between numbers and digits have a few numbers written down. Ex. 0, 5, 9 are all numbers but each one is a one digit number. 17, 35, and 62 are all numbers but each is made up of two digits.


After reviewing, have your child do a few. Ex. The number 27 is made up of how many digits? Which digit is all the way to the right? The digit all the way to the right is in the ones place. The one next to it will be in the tens place.

Practice this a few times.

(3)

Rounding to the tens place. Find the digit in the ones place. If the digit is 0, 1, 2, 3, or 4, then you round the digit in the ones place down to zero and leave the number in the tens place alone. Ex . 13 becomes 10 24 becomes 20


If the digit in the ones place is 5, 6, 7, 8, or 9 then the number in the ones place will become a zero but the number in the tens place will become one number higher. Ex. 17 becomes 20 26 becomes 30.

(4)

Estimations are good when they are only a few numbers away fro the actual value. You can explain that when a number is only two numbers or less away from the newly rounded number, then the estimate will be very close to the real answer. So this new value will be a good estimate.

Ex. 22 becomes 20 very close to the real number so good estimate.


If a number is far from the new rounded value then it may give a poor estimate.


Ex. 26 becomes 30 Estimate is not very close to the real value.


When rounded numbers are added together, there may be more discrepancies between estimations and actual values.

(5)

After rounding numbers to the tens place adding the new numbers together is much easier. The ones place is filled with zeros so all that really has to be added together are the digits in the tens place.

23 + 38 = ?


Ex. 23 becomes 20 and 38 becomes 40


20 + 40 = ___ Since both ones place have a zero, the answer will have a 0 in the ones place. So all that is left is to add the 2 and 4 which equal 6. Since the 2 and 4 were in the tens place, the number 6 will fill the tens place in the new answer.


20 + 40 = 60 and 23 + 38 = 61

The rounded values give a very close answer to the actual value so this is a good estimate.


25 + 45 = ? Rounding: 30 + 50 = 80


Actual value: 25 + 45 = 70


So the answer 80 would not be a good estimate because it is very far from the actual value.

Extra Help Problems

(1)

Rounding. This worksheet should include numbers that will be rounded up and down.

4 will be rounded to __

(2)

7 will be rounded to __

(3)

13 will be rounded to __

(4)

16 will be rounded to __

(5)

22 will be rounded to __

(6)

25 will be rounded to __

(7)

30 will be rounded to __

(8)

38 will be rounded to __

(9)

41 will be rounded to __

(10)

49 will be rounded to __

(11)

Is 40 a good estimate for the number 37 ? Yes or No

(12)

Is 40 a good estimate for the number 30 ? Yes or No

(13)

Is 50 a good estimate for the number 46 ? Yes or No

(14)

Is 50 a good estimate for the number 44 ? Yes or No

(15)

Is 60 a good estimate for the number 62 ? Yes or No

(16)

Is 60 a good estimate for the number 57 ? Yes or No

(17)

Is 70 a good estimate for the number 71 ? Yes or No

(18)

Is 70 a good estimate for the number 64 ? Yes or No

(19)

Is 80 a good estimate for the number 83 ? Yes or No

(20)

Is 80 a good estimate for the number 77 ? Yes or No

(21)

Is 90 a good estimate for the number 94 ? Yes or No

(22)

Is 90 a good estimate for the number 88 ? Yes or No

(23)

Is 30 a good estimate for the number 37 ? Yes or No

(24)

Is 20 a good estimate for the number 19 ? Yes or No

(25)

Is 10 a good estimate for the number 12 ? Yes or No

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