Subtraction with regrouping is necessary when the digit in the (top number) is smaller than the digit in the subtrahend (bottom number) within the same place value column.
Videos often use base-ten blocks or place value charts to show that the value of the number remains the same (e.g., changing 42 from "4 tens, 2 ones" to "3 tens, 12 ones"). 2. Key Instructional Strategies Subtraction with Regrouping - Math Video for 2nd Grade
To help students remember when to regroup, many videos use catchy rhymes or catchy visual cues: Subtraction with regrouping is necessary when the digit
Breaking numbers into tens and ones (e.g., 42 becomes ) to make the subtraction of each place value clearer. changing 42 from "4 tens