Adding and subtracting within 1,000

Using place value to add 3-digit numbers: part 1
Using place value to add 3-digit numbers: part 2
Adding 3-digit numbers
Add within 1000
Worked example: Subtracting 3-digit numbers (regrouping)
Subtracting 3-digit numbers (regrouping)
Worked example: Subtracting 3-digit numbers (regrouping from 0)
Subtract within 1000