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Lesson 1: Visually adding within 100

# Addition and subtraction with number lines

Sal figures out which number line matches up with a 2-digit addition or subtraction problem.

## Want to join the conversation?

• Are number lines only good for addition and subtraction? Or do they have other uses?
• Number lines can be an useful tool for looking at single-variable systems. I have used them in most Mathematics courses I have taken so far in college.
• can you use a penny to solve a problem
• maybe it depends on how you use the penny it would probably be good for measurement.
• DO we have to do the quiz over and over again
• No... when you do the Unit Test at the bottom of the page all the questions you get right it marks them as Mastered.
• what is 9+10024
• use this strategy OK? here it goes 10024+9= first add 4 and 9 its 13 so now 3 is there the 1 will add the 2 thats 3 and the 100 remains so now just combine the 33 with the 100 so its 10033 ok?
(1 vote)
• can we use pencils to count
• You can! You can also use any object to count.
• well just watch a video that relates to this then you can get better and you can have hints and you can just ya but just find a video that relates to this math/ khan academy.
• can anyone help me
• When you are adding, you go UP the number line. When you are subtracting, you go DOWN the number line.
(1 vote)
• Is that easy to do or not?