Subtract by Counting On - Up to 20
š§āāļø Climbing the number ladder! When two numbers are very close together on the number line, counting UP is faster than subtracting down.
Concept
We usually subtract by counting backward. But what if the problem is **18 - 15 = ?** Counting backward 15 spaces would take forever! Let's use a shortcut. šÆ **The "Distance" Shortcut:** When the numbers are close, just find the distance between them by counting UP from the small number to the big number! 1. **Start at the small number:** Start at 15. 2. **Count up to the big number:** Say "16, 17, 18". 3. **Count your steps:** How many steps did you take? You took 3 steps! So, **18 - 15 = 3**. You turned a subtraction problem into a much faster addition puzzle!
Try it
Let's climb the ladder and count up! **Instructions:** Start at the small number and count on to the big number to find the answer. **Problem 1: 19 - 17 = ?** * Start at 17. Count up to 19: "18, 19". * How many steps? ___ * Answer: 19 - 17 = ___ **Problem 2: 14 - 11 = ?** * Start at 11. Count up to 14. * Answer: ___ **Problem 3: 20 - 18 = ?** * Answer: ___ **Problem 4: 16 - 15 = ?** * Answer: ___