Chapter 4 Subtraction is Super
What we learned for adding in the last chapter we now apply to
subtraction. Adding is always the easier of the two, so subtraction
might need a little more attention. As with the adding chapter, here we
are going to focus on strategies that will help the children to be more
at ease with subtraction and that let the children perform those pesky
subtraction sentences in their heads. Again, we are going to demonstrate
and model the strategies that the mathematicians of the world do in
their heads in order to teach those who need a strategy. The same
caution applies as with the adding for those that have been using some
strategies already. Please just try the strategies and then use what
works for you. Subtract away!!!
1. Counting Back-
Just as with adding, counting back is a useful strategy that is to be
used when the number being subtracted is 1, 2 , or 3. In class, we say “
Put the first number in your head and count back” as we actually move
our hand in a backwards motion to give the visual and bodily learners a
concrete picture of what is happening.
Example: 6-2=
Put 6 in your head and count back 5, 4.
****CAUTION****
The big difference between adding and subtracting is that subtraction
HAS to be done in order that it appears. Please reinforce that
subtraction makes sense when the biggest number is in the front and the
smallest number is at the end.
2. Do Some Math Magic
Ok…the minute has passed and now we are
going to talk about how subtraction and addition is related. Just as
with reading if you can spell “cat” you can spell “fat”, if you know the
adding fact, then you know the subtraction fact. In class we say that
we are doing “magic”. In fact we get out a magic wand and say, “Hocus,
pocus. Alacazam…Poof!”
If you know 8 + 2 = 10 then...
you know 10 - 2 = 8
REMEMBER that when doing subtraction the biggest number is ALWAYS in the FRONT.
3. We love you ten!!!
That's right ten can help us with
subtraction as well. We can use a ten frame to help us subtract higher
numbers like this... (drumroll please )
So 15-8= could look like this...
First put 8 dogs in the ten frame
because we know that number and then add the bones to get to 15. If you
count how many bones then you can see how much 15-8 is. The possibilites are just endless!
Activities for Chapter 4 concepts
1. Using Strategies to Solve Facts
Materials: 10 counters and 10 different counters (e.g. red and blue)
Procedure:
1.
Create a line of 2 red counters and 4 blue counters. Have the child
separate the red counters from the blue counters and then remove the red
counters from sight. Ask “How many cubes are left?”
2. Draw a picture of what the child did by crossing out the counters.
3. Repeat by creating a new line of counters with some red and some blue. Discuss and draw a picture for what did.
4. Model how to count back when removing 1, 2, or 3 .
2. Related Fact Stories
Materials: 12 counters, cup
Procedure:
1.
One person writes a number from 1 to 12 on paper and counts out that
many counters. That person then hides some of the counters under the
cup.
2.
The partner uses the number on the paper and the number of counters
that are still out to determine the number of counters hidden under the
cup. The partner describes how he found the missing number.
3. Check the counters under the cup.
4. Reverse roles.
As the child is figuring out how many are under the cup try and have
her use the adding sentence or how many they started with to help figure
out how many are in the cup. For example, if there were 10 counters to
start and some are covered and there were 4 left, ask “4 plus how many
will get you 10?”