ADDITION SHORTCUTS & MATH TRICKS |
ADDITION SHORTCUTS & MATH TRICKS
1
Left-to-Right Addition
Add the tens digits first, then the units digits. This matches how we read numbers naturally!
Example: 48 + 35
1. Add tens: 40 + 30 = 70
2. Add units: 8 + 5 = 13
3. Combine: 70 + 13 = 83
Answer = 83
2
Round and Adjust (Compensation)
Round one number up to the nearest ten, add, and then subtract the difference you added.
Example: 57 + 39
1. Round 39 up to 40 (added 1)
2. Add: 57 + 40 = 97
3. Subtract 1: 97 - 1 = 96
Answer = 96
3
Grouping to Make Tens
When adding a string of numbers, look for pairs that add up to 10 or 100 first.
Example: 7 + 8 + 3 + 2
1. Group pairs: (7+3) = 10 and (8+2) = 10
2. Add groups: 10 + 10 = 20
Answer = 20
4
Adding Near 100 or 1,000
Break numbers down to easily add hundreds and adjust the remaining parts.
Example: 345 + 198
1. Treat 198 as 200 - 2
2. Add: 345 + 200 = 545
3. Subtract 2: 545 - 2 = 543
Answer = 543
5
Breaking by Place Value (Partitioning)
Split numbers into hundreds, tens, and units to add larger numbers mentally.
Example: 324 + 153
1. Hundreds: 300 + 100 = 400
2. Tens: 20 + 50 = 70
3. Units: 4 + 3 = 7
Total = 400 + 70 + 7 = 477
6
Adding Sequence (1 to N)
To add numbers from 1 up to N, use the formula: N × (N + 1) ÷ 2
Example: 1 + 2 + 3 + ... + 10
1. N = 10
2. N + 1 = 11
3. Multiply & divide: (10 × 11) ÷ 2 = 110 ÷ 2
Answer = 55