7. Mental Addition Tricks
Mental Addition Tricks
Master fast calculations in your head.
1. The „Left-to-Right“ Method
In school, we learn to add from right to left. For mental math, Left-to-Right is much faster because it follows the way we read numbers.
| Calculation | Step 1 (Tens) | Step 2 (Ones) | Result |
|---|---|---|---|
| 45 + 37 | 40 + 30 = 70 | 5 + 7 = 12 | 70 + 12 = 82 |
| 68 + 24 | 60 + 20 = 80 | 8 + 4 = 12 | 80 + 12 = 92 |
2. Making Tens (Rounding)
If a number is close to a „round“ number (like 10, 20, 50), add the round number first and then subtract the difference.
Example: 58 + 25
58 is close to 60.
1. Add 60 + 25 = 85
2. Subtract the 2 we added: 85 – 2 = 83
58 is close to 60.
1. Add 60 + 25 = 85
2. Subtract the 2 we added: 85 – 2 = 83
3. Break-Apart Strategy
Keep the first number whole and break the second number into its components.
- Task: 125 + 46
- Add the tens: 125 + 40 = 165
- Add the ones: 165 + 6 = 171
Quick Practice Table
| Trick | Equation | Mental Path |
|---|---|---|
| Rounding | 49 + 17 | 50 + 17 – 1 = 66 |
| Breaking | 84 + 32 | 84 + 30 + 2 = 116 |
