Lesson 2 4 Subtracting Integers with Tiles When

Lesson 2. 4 Subtracting Integers with Tiles

�When we added integers using tiles, we combined the tiles together. �When we subtract, we remove tiles from a group.

�Remember that equal numbers of red and yellow model 0. �Adding a zero pair to a set of tiles does not change its value.

�To use tiles to subtract integers, model the integer first, then take away the number of tiles indicated by the second integer.

�(+5) – (+9) Model +5 There are not enough tiles to take away 9. We need 4 more tiles. . .

�We can add zero pairs without changing the value of the equation. Add 4 yellow tiles. . . then add 4 red tiles. �We can now take away 9 yellow tiles. �Only 4 red tiles remain. (+5) + (+9) = -4 This is a subtraction equation. . .

(-2) – (-6) = Model -2. There are not enough tiles to take away -6. Add enough zero pairs to be able to take away -6. Now, we can take 6 red tiles away. Then we write: (-2) – (-6) = +4

�(-6) – (+2) Model -6 In this example, there are no yellow tiles to take away. So, add two zero pairs. Take away the two yellow tiles. There are 8 red tiles left. . . Then you have (-6) – (+2) = -8

�(+2) + (-6) Model +2 �There are no red tiles to take away at first. So, add zero pairs. Then take away 6 red tiles. �Since 8 yellow tiles remain, the answer is +8.

Homework �Workbook 2. 4 �Textbook Page 69 -70 #2, 5, 7 and Reflect