Help children understand the core elements of two digit regrouping by using simplistic worksheets after going through the basic process with them. Teach them that each unit in the tens section is actually equivalent to ten units in the ones section. Show them how this can be used to help you subtract a larger number from a smaller one. Steal a ten from the tens column and use it to make the smaller number larger. Complete the subtraction in this way. Give the children worksheets such as “Monster Math” and “Subtraction” to let them practice.
Using money problems is an effective way to show how mathematical concepts can relate to the real world. Get students to work out the correct amount of change when 75 cents is used to pay for a 50 cent bag of sweets, for example. This helps children practice regrouping across 0 as well, which can confuse some students. Use worksheets such as “Subtracting Money” to give them a chance to practice. Convert the non two-digit problems into two digit ones if you wish. Third graders should be comfortable subtracting any numbers up to 10,000, however, so this shouldn’t be an issue.
Use more hands on subtraction activities when students have trouble with understanding the concepts with just numbers. Find over 100 small stones to use as props for one such activity. You can also use matchsticks if they are easier to obtain. Create groups of tens with your units and then create a two-digit subtraction problem using them. Use spare units to make up the ones section of the problem. The children can literally bring a group of tens over from the tens pile and split them up into ten ones. Children should understand the process much more easily when it is shown is this way.
When children have understtod the basics of two-digit regrouping subtraction, you can use games to help the children gain confidence. Use a game like “Math Flash Cards,” set to give two digit subtraction problems, and see how quickly students can answer in ten seconds. The game takes an average speed per question. See which students can get the quickest average time with fewest mistakes. This can help cement the ideas in their minds.