## unit 4 parent letter

## regrouping

Examples for Addition- Trade 10 units (ones) for 1 rod (ten). - Trade 10 rods (tens) for 1 flat (hundred). - Trade 10 flats (hundreds) for 1 cube (thousand). |
Examples for Subtraction- Trade 1 cube (thousand) for 10 flats (hundreds).- Trade 1 flat (hundred) for 10 rods (tens). - Trade 1 rod (ten) for 10 units (ones). |

## Addition strategies

When adding, it is best to use one of these three strategies -

- Base Ten Model

- Expanded Form

- Open Number Line

- Base Ten Model

- Expanded Form

- Open Number Line

## Subtraction strategies

When subtracting, it is best to use one of these three strategies -

- Base Ten Model

- Expanded Form (if the problem doesn't involve regrouping)

- Open Number Line

- Base Ten Model

- Expanded Form (if the problem doesn't involve regrouping)

- Open Number Line

__Strategy 3: Open Number Line__

- Start at the lower/est number at the BEGINNING of the open number line and count UP (Number Line Liam).

- Start at the higher/est number at the END of the open number line and count BACK (Jump, Hop, Step)