Chapter 8 Adding and Subtraction Has Just Gotten Bigger!
Chapter 8- Adding and Subtracting Has Just Gotten BIGGER!!
Can you believe that this is the same child that started in the
beginning of the year just learning how to make numbers? Well we are
kicking things up a HUGE notch to get ready for Second Grade. This
chapter introduces finding the sums and differences of TWO- digit
numbers without regrouping (or trading in) and two- digit and one-digit
numbers with regrouping (trading in). WOW!! Can you believe it? We have
been training hard for this and now the day is here to put all that we
have learned to the test. Take things slow and easy and we all will
emerge victorious!! Use this website to help practice at home.
http://www.kyrene.org/mathtools/
VOCABULARY
ones - the value of a digit in the ones position on a place value chart
tens - a group of ten ones otherwise known as a bundle
1. Addition -
· Adding groups of 10 is the almost the same as adding numbers less than 10.
· When adding tens to a two –digit number, only the TENS digit changes. An example of this is 3 7 +10 = 4
7. When we were doing this with money we would say that “A dime is 10
so change the tens”. The same idea applies here. We should be able to
get through these no sweat!
·
When adding two digit numbers ALWAYS, ALWAYS, ALWAYS count the ones
side first and only add the ones to the ones and the tens to the tens.
Here is an example:
21
+18
9 ( 1 + 8 = 9)
30 ( 20 + 10 = 30)
39
This is the process that actually is going on in the child’s head. We
do not teach this way because then we would lose our minds. 
Instead we use tens and ones sticks first while I am writing on the
board the traditional way like written above. Doing this together lets
the children see the concrete version that they need with the written
way that will be the way that they will be dong this in the future. It
also allows every learner to use what they need to figure out the
equation. We make a BIG deal about counting the ones first because there
will be a time when we will have to trade in for a ten… but not yet.
When there is 9 or less in the ones we say that we are “Safe” 
and then move on to adding the rest. When I am writing it on the board I
actually draw a line down the middle of the equation so that the
children can see each side as different.
45
+12
-------
Anyway that works for your child is fine by me!!
· Now we are there for “trading in”. When there are 10 or more in the ones we sound the alarm, “ WOO, WOO, WOO” 
and trade in the ten ones for a tens stick. We actually pick up the ten
ones first then put them back and at the same time pick up a tens
stick. It is not allowed to have a ten or more ones in the ones side. L
2. Subtraction
The same rules apply to subtraction, yet this always seems to be an
area where children can get pretty tricked up. The key here is to take
your time and go slow so that the concepts get in those brains.
.
· Subtracting groups of 10 is the almost the same as adding numbers less than 10.
· When subtracting tens to a two –digit number, only the TENS digit changes. An example of this is 3 7 - 10 = 2 7. We should be able to get through these no sweat after working with all of those adding ones that are the same idea!
·
When subtracting two digit numbers ALWAYS, ALWAYS, ALWAYS count the
ones side first and only subtract the ones from the ones and the tens
from the tens. Does this sound familiar?
Again, we use tens and ones sticks first while I am writing on the
board the traditional way like written above. Doing this together lets
the children see the concrete version that they need with the written
way that will be the way that they will be dong this in the future. It
also allows every learner to use what they need to figure out the
equation. We make a BIG deal about counting the ones first because there
will be a time when we will have to trade in for a ten… but not yet.
When there is 9 or less in the ones we say that we are “Safe”
and then move on to adding the rest. When I am writing it on the board I
actually draw a line down the middle of the equation so that the
children can see each side as different.
45
-12
-------
Anyway that works for your child is fine by me!!
·
Here comes the tricky part. When count the ones first there are times
when we do not have enough ones to finish out the equation, Again, we
sound the alarm and pick up the 10 stick and trade it in for 10 ones and
out them on the tens side. I know that it seems like we are going
against the rules here, but it is only for a short time so we can get
away with it.
This is the area where there are a lot of mistakes, so if you can
practice at home with the tens and ones or dimes and pennies instead of
crossing off as we all learned to do that would be extremely helpful.
Activities for Chapter 12
1. Different Ways to Add and Subtract
Materials: connecting cubes or tens and ones materials or dimes and pennies.
Procedure:
1.
Write 20 + 15 on a piece of paper and tell a simple adding story
problem such as : “ I started the game with 20 marbles. Then I won 15
more marbles. How many marbles do I have altogether?”
2. Ask the child how you can use the cubes or tens and ones or dimes and pennies to solve the problem.
3. Have the child explain how he used the cubes and then write with the child how it would look with the numbers.
4.
Repeat with a simple subtraction story such as: “There were 36 horses
in the barn. 15 horses ran into the field. How many horses are left in
the barn?
5. It is also helpful to discuss what key words are letting the child know if he should add or subtract.
3. Expanded Addition
Materials: connecting cubes or tens and ones or dimes and pennies
Procedure:
1. Write 14 + 11 and 25 +17 on a piece of paper.
2. Have the child use the items to demonstrate each problem.
3. The child then solves each problem and explains how he solved using pictures, numbers and words.
4. Make sure that the child is counting the ONES first each time and sounds the alarm if he has to trade in for a ten.