Open Number Line Mats
Congratulations on your purchase of these Really
Good Stuff® Open Number Line Mats—a versatile
and open-ended tool for solving a variety of addition
and subtraction problems.
This Really Good Stuff® product includes:
• 6 Open Number Line Mats, Write Again®
wipe-off laminate
• This Really Good Stuff® Activity Guide
Introducing the Open Number Line Mats
Before introducing the Open Number Line Mats,
make copies of this Really Good Stuff® Activity
Guide and file the pages for future use. Or, download
another copy of it from our Web site at
www.reallygoodstuff.com. Always use a dry erase
marker on the Mats in order to preserve their Write
Again® wipe-off laminate surface.
Explain to students that they will be using a number
line in a new way to help them solve addition and
subtraction problems. Remind students that they
first used number lines to help them skip count and
to add, and then they learned to go backward along
a number line to help them subtract. Indicate that
now that they are working with bigger numbers (or
fractions, or decimals, or integers, and so forth),
they will use a number line to help them solve
problems with addition and subtraction, but in a
different way.
Ask students what the highest and lowest numbers
along a number line are. On the board, draw a line
with an arrow on each end, and show students how
a number line goes on forever in both directions.
Explain to students that because of this, they can
create number lines that start anywhere along the
continuum. Tell students these are called “open
number lines,” because when they label them they
can begin at any number.
Display the following problem:
By twelve o’clock, Brian had collected $150 from the
can drive. He collected another $132 by the end of
the drive. How much money did Brian collect
altogether?
Ask students what number sentence would reflect
this problem. Write 150 + 132 = on the board, above
your demo number line. Explain to students that
instead of starting to label your number line at 0
you are going to begin the number line at 150—the
bigger of the two numbers—then label your demo
open number line with 150. Indicate that you are
using the larger number in the problem as your
starting point.
Tell students that you are going to solve an addition
problem, and ask students what direction along the
number line you will be moving. After students
respond “up,” mark an exaggerated arrow on the
right-hand end of the open number line.
Explain to students that you are going to use
“landmark” numbers or rounded “friendly” numbers
to help you solve the problem. Ask students to break
apart the addend 132. And write the numbers 100
and 32, beneath 132. Explain to students that you
can use the 100, to jump up to 250 along the open
number line. Draw a large “jump” along the number
line, cross out the 100, and label the jump you made
with 100.
All activity guides can be found online:
Helping Teachers Make A Difference®
© 2011 Really Good Stuff
®
1-800-366-1920 www.reallygoodstuff.com Made in USA #159667
Open Number Line Mats
Ask students to tell you what they think the next
step should be. If necessary, explain that you can
use friendly numbers to break the problem down
further, by counting by tens to solve the remainder
of the problem. Starting at the 250, draw a smaller
jump up the line, and label it with 10. Ask students
where you are now along the number line, and record
260 below the line. Make two more jumps of 10,
recording 270 and 280 beneath the line. Make a
final, even smaller jump, label it with 2, and record
282 beneath the line. Circle 282 and complete the
number sentence.
Practicing with the Open Number Line Mats
Distribute an Open Number Line Mat and dry erase
marker to each student, and display the following
problem:
Lara needed 364 inches of ribbon for her party
favors. She found she only had 128 inches. How
many more inches of ribbon would she need to get?
Ask students to tell you what the question is
asking. If necessary, explain that the question is
asking them to find the difference between 364 and
128. Tell students to record 364 – 128 = in the
white box on their Mats. Ask students which
direction they need to move along the open number
line if the problem involves subtraction. If necessary,
remind them that they are to move down the
number line. Instruct students to use their dry
erase markers to emphasize the arrow on the lefthand side of their open number lines. Explain to
Helping Teachers Make A Difference®
students that they should record the bigger number
from the problem first and that because they will be
making jumps down the number line, they are to
record the 364 on the right side of the open number
line. Ask students to use “friendly numbers” to help
them find the easiest way to jump 128 down the
open number line. Tell students to break apart 128,
explaining that 100 and 28 are one way, then have
them record this under their number sentence. Ask
students where they would land if they made a jump
of 100 down the number line. Instruct students to
record the 264 beneath the number line and to
cross out the 100 beneath the number sentence.
Show students how 28 would equal two groups of 10
and another 8. You may find students using
different strategies as they work with the open
number line. For example, as in the example above,
students may find it easier to break apart the 8
into two 4’s, because it will get them to the friendly
number 240 by only making the first jump of 4. Use
these opportunities to encourage students to share
their strategies with each other to open up their
problem-solving options.
© 2011 Really Good Stuff® 1-800-366-1920 www.reallygoodstuff.com Made in USA #159667