Open Number Lines

Oscar has super strength. Just look at his muscles!

Oscar is holding 26 computers. Oh, no! Oscar dropped 7 computers. How many is he holding now?

Let’s use this open number line to subtract 26 minus 7. Open number lines are number lines without any numbers. We can use open number lines to add or subtract. We jump to the right to add and to the left to subtract.

26 is the whole in this subtraction sentence. Let’s write it under this dot. 7 is the part. This is the number of jumps we’ll make from 26. Remember, we jump to the left to subtract.

Great job! Now we can label the number line where each jump touches the number line. The difference is the number that the last jump lands on.

That means 26 minus 7 equals 19.

Okay, Oscar. Now that we know how strong you are, let’s see if you can hold something even heavier than computers. What’s heavier than computers? A couch!

Oscar is holding 15 couches. Then he adds 4 more. How many couches is Oscar holding altogether?

Let’s use this open number line to add 15 plus 4.

15 is the larger addend in this addition sentence, so let’s write it under this dot. 4 is the smaller addend. This is the number of jumps we’ll make from 15. Since we’re adding this time, we’ll jump to the right.

Nice work! Let’s write a number where each jump touches the number line. The sum is the number that the last jump lands on.

We did it! Oscar is holding 19 couches because 15 plus 4 equals 19.