Kindergarten - Checking Answers

 
     
 
     
 
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K
Problem Solving
Checking Answers
Make precise calculations and check the validity of the results in the context of the problem
Be able to perform calculations to find the exact answers. Use answers to double check calculations. Know how to re-work problem using answer to double check result.
 

Sample Problems

(1)

What is 4+2 =

(2)

Double check the answer by subtracting 6-4 =

(3)

What is 9-5=

(4)

Double check by adding 4+5=

Learning Tips

(1)

Double checking answers is very important and at times can be a bit confusing to children. Showing the steps taken is very important as well as explaining the reason behind it. Addition problems are straight forward. The solution is always equal or greater than the biggest number in the problem. The answer cannot be less. Point this out to your child. To double check the answer, the student can add the numbers again but this may produce the same number even if the answer is incorrect. Children tend to repeat their mistakes if they repeat the same process. So to double check the answer, the opposite procedure is worked out using the same numbers.


Ex. 10 + 2 = 12 To double check, take the answer, 12, and subtract the smaller of the two numbers, 2. The reason I choose the smaller of the two numbers is because it is usually simpler than subtracting the larger number. The result should give you the other number used in the original problem, 10.


12 – 2 = 10 If this works then the original answer of 12 is correct. If the answer does not give you the expected answer then the answer to the original addition problem is incorrect. Explain the logic behind using the same numbers and also demonstrate this using real objects.

(2)

Subtraction problems are a bit easier as there is only one way to double check.


Ex. 10 – 2 = 8 To double check, Take the answer, 8, and add it to the number that was subtracted, 2, from the original number, 10.


8 + 2 = 10 The answer should give you the first number. If the answer is different from what was expected, then the original answer to the subtraction problem is incorrect. Explain the logic behind using the same numbers and also demonstrate this using real objects.

(3)

Number patterns are usually addition, subtraction, or counting problems at this level. If the pattern is an addition pattern, then subtracting by the number being used to set the pattern is how to double check the pattern.

Ex. 10, 13, 16, 19, 22 Three is being added to the numbers. So we would subtract three from the numbers. The pattern would now be backwards but should give us the same numbers. Start with the last number given in the sequence.


22 – 3 = 19 19 – 3 = 16 16 – 3 = 13 13 – 3 = 10 (The numbers should be the same as the ones in the original pattern).


If the pattern is an subtraction pattern, then adding by the number being used to set the pattern is how to double check the pattern.

Ex. 15, 11, 7, 3 Four is being subtracted from the numbers. So we would add four to the numbers. The pattern would now be forwards but should give us the same numbers. Start with the last number given in the sequence.

Ex. 3 + 4 = 7 7 + 4 = 11 11 + 4 = 15 (The numbers should be the same as the ones in the original pattern).


(4)

Money: When working with money, it is important to gather all similar coins together. This will help in counting it. After gathering like coins, the student will add them together. To double check, each coin will be subtracted from the dollar amount. It may be easier to subtract nickels, dimes, or pennies first. Start with the coin of the least value first and work your way up.


Ex. 2 quarters, 1 dime, 3 nickels, and 2 pennies = $0.77 or 77 cents


$0.77 - $0.02 (pennies) = $0.75 $0.75- $0.15 (nickels)= $0.60


$0.60- $0.10 (dime)= $0.50 (which is the remaining two quarters).


Although I subtracted the groups of coins, you and your child may subtract individual coins.

(5)

Time: At this point they are working on telling time to the hour. This is generally done by moving the smaller hand and the minute hand (although it does move) appears to stay in the same place. Explain since that every hour the minute hand moves around the clock once and ends up in the same spot. For every hour the little hand moves forward or backward one number and the minute hand remains on the same number. To double check, move the hour hand in the opposite direction that the problem asked you to move it.


Ex. It was three o’clock one hour ago. What time is it now? The answer is four o’clock. To double check this answer we will move the hand back one space for the one hour. The hour hand is pointing to the four so we will move it back to the three. The minute hand will stay in its place.

Extra Help Problems

(1)

Double check the following problems. Fill in the blnk with the correct number.

4+5=9

9-_=4

(2)

6+6=12

12-6=_

(3)

10+5=15

_-5=10

(4)

20+2=22

22-_=20

(5)

10-3=7

7+3=_

(6)

15-4=11

11+4=_

(7)

23-5+18

18+5=_

(8)

14-7=7

7+7=_

(9)

It was 8 o’clock two hours ago. It is ten o’clock right now.

Move the ________ hand two numbers backwards to check answer.

(10)

It is 2:30 p.m. now. It will be 5:30 p.m. in three hours.

Move the ________ hand three numbers forward to check answer.

(11)

Four dimes equal $0.40. To double check my answer I will:

Add the dimes again Subtract counting by tens

(12)

Two quarters and one dime equal $0.60. To double check my answer I will : Add the money again Subtract the coins.

 

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