Use Models to Subtract 2-Digit Numbers (No Regrouping)
āļø Cross out the blocks! When both numbers are two digits long, you have to cross out BOTH Tens-Rods and Ones-Cubes.
Concept
Drawing pictures is brilliant for checking your work and seeing exactly what subtraction looks like. šÆ **The "Double Cross Out" Method:** **Example: 56 - 24 = ?** 1. **Draw the starting number (56):** Draw 5 Tens-Rods and 6 Ones-Cubes. | | | | | . . . . . . 2. **Cross out the Ones first!** Subtraction number is 24. It has 4 ones. Cross out 4 little dots with X's. (You have 2 dots safe). 3. **Cross out the Tens next!** The number is 24. It has 2 tens. Cross out 2 long Rods with X's! (You have 3 Rods safe). 4. **Count the survivors!** You have 3 Rods and 2 Cubes perfectly safe. 5. **Answer:** **32**! You "subtracted 24" physically!
Try it
Double cross-out time! **Instructions:** Imagine the big blocks and little blocks for the first number. Cross out the the blocks from the second number to find the answer. **Problem 1: 48 - 15 = ?** * Model: 4 Rods, 8 Cubes. * Cross out 5 Cubes. (Leaves ___) * Cross out 1 Rod. (Leaves ___) * Answer: ___ Rods and ___ Cubes = ___ **Problem 2: 67 - 32 = ?** * Answer: ___ **Problem 3: 89 - 56 = ?** * Answer: ___ **Problem 4: 25 - 11 = ?** * Answer: ___