Break Apart a 2-Digit Number to Subtract
šŖ The Reverse Splitting Spell! Break exactly ONE number apart in your mind to make subtraction incredibly fast.
Concept
When doing mental subtraction, breaking BOTH numbers down can be risky. The safest trick is to lock the big number and just break the number you are taking away! šÆ **The "Hold and Break" Strategy:** **Example: 68 - 35 = ?** To do this in your head quickly without paper: 1. **Hold the Big Number:** Lock the number **68** in your brain. 2. **Break the Taker:** 35 is made of **30** and **5**. 3. **Subtract the Tens first:** 68 minus 30. (Change the tens!). 68 -> 58 -> 48 -> 38. That's **38**. 4. **Subtract the Ones to finish:** 38 minus 5. (8 - 5 = 3). That's **33**. So, **68 - 35 = 33**. This is the exact same math as the jumping frog on the number line, just without drawing the jumps.
Try it
Hold the big number, break the small one! **Instructions:** Subtract the tens of the small number. Then subtract the ones. **Problem 1: 86 - 42 = ?** * Hold 86. * Subtract 40: 86 - 40 = ___ * Subtract 2: ___ - 2 = ___ * Answer: ___ **Problem 2: 59 - 25 = ?** * Hold 59. * Subtract 20: ___ * Subtract 5: ___ * Answer: ___ **Problem 3: 77 - 31 = ?** * Answer: ___ **Problem 4: 98 - 63 = ?** * Answer: ___