Seeing Sums Activity

How could we model the problem 6 – 4? Apples anyone?

The Set Model for addition and subtraction works... X 6 − 4 = 2 Poster Problems - Seeing Sums Slide #1

Does this model still work when we need to take away more than we have Does this model still work when we need to take away more than we have? What happens when we try to model 6 – 8?

...Except when you try to “take away” more than you have 6 − 8 = ? Poster Problems - Seeing Sums Slide #2

What does it mean to take away something we don’t even have?

If only there was a model that worked for all scenarios… …

Poster Problems - Seeing Sums Slide #3

Number Line Models for Sums and Differences Example: -3 – (-7) = ? -15 -10 -5 0 5 10 15 Example: -3 – (-7) = ? Any ideas? Poster Problems - Seeing Sums Slide #4

Be sure to keep these tips in mind while you work. For each upcoming problem, the number line shown. Be sure to watch the in class demonstration carefully, it will show you how to create and manipulate the arrows on your number lines. Be sure to keep these tips in mind while you work. Always start your arrows from zero. Always start by drawing the arrow for the first number in the problem. Remember to start at zero when drawing the arrow for the second number. Arrows for positive numbers should point to the right. Arrows for negative numbers should point to the left. After you have drawn both arrows from zero, move the tail of your second arrow to the head of your first arrow. The answer will be at the end of the second arrow. Remember to rotate your second arrow when subtracting.

4 + 7 = 4) -2 + (-5) = -5 + 7 = 5) -3 – (-7) = 8 – 11 = 6) 4 – (-6) = -15 -10 -5 0 5 10 15 4 + 7 = 4) -2 + (-5) = -5 + 7 = 5) -3 – (-7) = 8 – 11 = 6) 4 – (-6) =