Welcome to a lesson on adding integers using
the number line.
Before we look at some examples, let's review
the vocabulary for addition.
Welcome to a lesson on adding integers using
the number line. Before we look at some examples,
let's review the vocabulary for addition.
In the addition problem a + b = c, a and b
are the addends and c is the sum. So for 5
+ 2 = 7, 5 and 2 are the addends and 7 is
the sum. And now let's use the number line
to determine the sum of integers. We will
first use a number line to determine nine
plus negative 7. We will use an online number
line tool to determine the sums. We begin
by modeling positive 9. To do this, we take
this bottom point and move it right 9 units
to positive 9. And because we have 9 plus
negative 7, from positive 9, we move the top
point left 7 units. Whenever we add a negative
integers, we move left. Whenever we add a
positive integers, we move right. So because
we have plus negative 7, we move the top point
left 7 units. So 1, 2, 3, 4, 5, 6, 7 units
to the left. Notice how we are now at positive
2 on the number line, which gives us the sum.
9 plus negative 7 equals positive 2. Now let's
determine negative 9 plus 7 using the number
line. We begin by modeling negative 9 by moving
the lower point left 9 units to negative 9
on the number line. And because we are adding
positive 7, we move the top point right 7
units. 1, 2, 3, 4, 5, 6, 7. Notice how we
are not at negative 2 on the number line,
which gives us the sum. Negative 9 plus 7
equals negative 2. Let's look at two more
examples. Using the number line, we want to
determine negative 4 plus negative 5. We begin
by modeling negative 4 on the number line
by moving the lower point left 4 units to
negative 4 on the number line. From here because
we are adding negative 5, we move the top
point left 5 units. So 1, 2, 3, 4, 5. Notice
we are now at negative 9 on the number line,
which is the sum. Negative 4 plus negative
5 equals negative 9. And now for the last
example we have 5 plus 4, which we probably
do not need a number line to determine, but
let's go ahead and show it. We begin by modeling
positive 5 on the number line by moving the
lower point right 5 units to positive 5 on
the number line. Because we are adding positive
4 we move the top point 4 units to the right
from positive 5. 1, 2, 3, 4. We are now at
positive 9 on the number line, which is the
sum. 5 plus 4 equals 9.
I hope you found this helpful.
