Children use their developing understanding of counting forwards and backwards by 10s and 100s, explaining which digit changes and why (Place Value 16, Patterns and Algebra 12), and Standard and non-standard place value of, and partitioning three-digit Numbers (Place Value 17) to investigate adding and subtracting three- and four-digit numbers using place value and compensation.
As children are investigating adding and subtracting, they continue to investigate these place value concepts.

Compensation starts at the following time stamps: Add 3-digit 5:55  Subtract 3-digit 5:19  Add 4-digit 6:36   Subtract 4-digit 7:12