Welcome to this video on how to use a number
line.
Using a number line can be useful when you’re
adding and subtracting numbers.
Let’s take a look at a problem.
Lacy has 9 pieces of gum.
She gave two pieces to her friend Martha in
first period.
In second period, she gave 1 piece each to
Jonathan, and Casey.
In her last period she gave a piece to each
of her three lab partners.
When Lacy’s mom picked her up from school
she gave her a new pack of gum with 10 pieces in it.
How many pieces of gum does Lacy now have
total?
Let’s start by drawing our number line.
Now, let’s read back through our problem and follow what happens with the gum on our number line.
When we start, Lacy has 9 pieces of gum.
Then, she gave two pieces to her friend Martha
in first period, so we go back on our number line.
She gave them away, so now she is missing
two pieces.
We go back two spots on the number line so
she has seven.
What happens next?
In second period, she gave one piece each
to Jonathan and Casey.
She gave one piece to Jonathan and one piece
to Casey; she gave away two more pieces.
We have to go to the left two more times on
our number line.
Now she’s at 5 pieces.
Then what happens?
In her last period, she gave a piece to each
of her three lab partners.
She gave one piece to three different people,
so that’s minus three pieces of gum.
We go to the left three spots
on our number
line, which puts us at two.
Then what happens?
When Lacy’s mom picked her up from school,
she gave her a new pack of gum with 10 pieces in it.
How many pieces does Lacy have left?
Her mom gave her 10 new pieces, so we’re
adding 10 on to the 2 that we have right here.
We need to go to the right 10 places on our
number line.
That’s going to put us all the way over
here at 12.
At the end of the day, Lacy’s mom comes
to the rescue and gives her 10 more pieces.
She ends up with more pieces than she had
at the beginning.
Number lines can be really useful to help
you visualize changes taking place and to
help you keep track of where you are at in
your word problem.
I hope that this video was helpful!
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See you next time!
