Subtract 3-Digit Models (With Regrouping!)
šØ Break out the sledgehammer! You don't have enough Ones cubes... so you have to smash a Rod. You don't have enough Rods... so you have to smash a giant Square Flat!
Concept
Here is exactly what "Borrowing" looks like in the real world. šÆ **The Double Smash Rule:** **Problem: 312 - 145 = ?** * Start: 3 Flats, 1 Rod, 2 Cubes. 1. **Subtract 5 Cubes?** Can't! I only have 2. **Smash a Rod!** (Take the 1 Rod, smash it to 10 cubes). Now I have 0 Rods, and 12 Cubes. Cross out 5 cubes. (12 - 5 = 7 left). 2. **Subtract 4 Rods?** Can't! I only have 0! **Smash a Flat!** Take 1 Giant Flat and smash it into 10 Long Rods! Now I have 2 Flats and 10 Rods. Cross out 4 Rods! (10 - 4 = 6 left). 3. **Subtract 1 Flat:** Cross out 1 flat. (2 - 1 = 1 left). 4. **Answer:** 1 Flat, 6 Rods, 7 Cubes. **167**!
Try it
Smash to survive! **Instructions:** Imagine smashing the block to get 10 smaller pieces. **Problem 1: 451 - 138 = ?** * Cubes (1 - 8). Smash a rod! (Make 11 cubes). 11 - 8 = 3. * Rods: We smashed one, so there are 4 left. 4 - 3 = 1. * Flats: 4 - 1 = 3. * Answer: ___ **Problem 2: 524 - 162 = ?** * Cubes: 4 - 2 = 2. (Safe! No smashing needed). * Rods: 2 - 6. Smash a Flat! Make 12 Rods. 12 - 6 = ___ * Flats: (We smashed one, so 4 left). 4 - 1 = ___ * Answer: ___ **Problem 3: 315 - 182** * Answer: ___