Count On and Use Ten to Subtract - Up to 20
ā”ļø The ultimate combination! Let's put two mighty strategies together to solve any teen subtraction problem in record time.
Concept
You know how to "Count On", and you know how to use "Ten as a stepping stone". Let's put them together! šÆ **The Combo Strategy:** **Example: 14 - 8 = ?** We can count UP from 8 to 14, but we'll use 10 as a rest stop to make it faster. 1. **Count up from the small number to 10:** How many steps from 8 to 10? It's 2 steps. 2. **Count up from 10 to the big number:** How many steps from 10 to 14? It's 4 steps. 3. **Add your steps together!** 2 steps + 4 steps = 6 total steps. So, **14 - 8 = 6**. This is the fastest mental math trick for hard subtraction problems!
Try it
Let's combo our strategies! **Instructions:** Find the steps to 10, then the steps past 10, and add them together. **Problem 1: 15 - 9 = ?** * Steps from 9 to 10: 1 * Steps from 10 to 15: 5 * Add them up! 1 + 5 = ___ * Answer: 15 - 9 = ___ **Problem 2: 13 - 7 = ?** * Steps from 7 to 10: ___ * Steps from 10 to 13: ___ * Add them: ___ + ___ = ___ * Answer: 13 - 7 = ___ **Problem 3: 16 - 8 = ?** * Answer: ___ **Problem 4: 12 - 9 = ?** * Answer: ___