Transcript 6 − 4 = 2 - Cloudfront.net

Seeing Sums Activity
How could we model
the problem 6 – 4?
Apples anyone?
The Set Model for addition and
subtraction works...
X
XX
X
6−4=2
Poster Problems - Seeing Sums Slide #1
Does this model still
work when we need to
take away more than
we have?
What happens when
we try to model 6 – 8?
...Except when you try to “take away”
more than you have
XXX
XX
X
XX
6−8=?
Poster Problems - Seeing Sums Slide #2
What does it mean to
take away something
we don’t even have?
If only there was a
model that worked for
all scenarios… …
QuickTime™ and a
JVT/AVC Coding decompressor
are needed to see this picture.
Poster Problems - Seeing Sums Slide #3
Number Line Models
for Sums
and Differences
-15
-10
-5
0
5
Example: -3 – (-7) = ?
Any ideas?
Poster Problems - Seeing Sums Slide #4
10
15
For each upcoming problem, the number line shown. Be sure to
watch the in class demonstration carefully, it will show you how
to create and manipulate the arrows on your number lines.
Be sure to keep these tips in mind while you work.
• Always start your arrows from zero.
• Always start by drawing the arrow for the first number in
the problem.
• Remember to start at zero when drawing the arrow for the
second number.
• Arrows for positive numbers should point to the right.
• Arrows for negative numbers should point to the left.
• After you have drawn both arrows from zero, move the tail
of your second arrow to the head of your first arrow. The
answer will be at the end of the second arrow.
• Remember to rotate your second arrow when subtracting.
-15
-10
-5
0
5
10
15
1)4 + 7 =
4) -2 + (-5) =
2)-5 + 7 =
5) -3 – (-7) =
3)8 – 11 =
6) 4 – (-6) =