It is common for students to regroup numbers when they add multi-digit numbers. They understand that one hundred is ten tens, one ten is ten ones, and so forth. Use add 6-digit and 4-digit numbers with regrouping worksheet to help your students practice this concept and develop their conceptual and strategic knowledge. In each problem, the numbers are laid out in the horizontal format. Students should try to use different strategies involving composing and decomposing numbers to solve these problems. This will help them develop flexibility and fluency.