Left-to-Right Mental Subtraction

Left-to-Right Subtraction

Just like addition, subtraction is easier left-to-right for mental math!

The Method

Example: 847 - 263

Think left to right:

1. Hundreds: 800 - 200 = 600
2. Tens: 40 - 60 = need to borrow
   • Take 100 from the 600: 500
   • Now: 140 - 60 = 80 → 580
3. Ones: 7 - 3 = 4 → 584

When No Borrowing Needed

Example: 586 - 231

• 500 - 200 = 300
• 80 - 30 = 50 → 350
• 6 - 1 = 5 → 355

Super fast!

With Borrowing

Example: 734 - 258

1. 700 - 200 = 500
2. 34 - 58 = need to borrow
   • Borrow 100: 400 remaining
   • 134 - 58 = 76 → 476

Or combine last two steps mentally.

Running Subtraction

Example: 542 - 137

Start with 542, subtract parts:

• 542 - 100 = 442
• 442 - 30 = 412
• 412 - 7 = 405

Comparison with Right-to-Left

Traditional (right-to-left): 542 - 137

• 2 - 7: can't do it, borrow...
• 12 - 7 = 5
• 3 - 3 = 0 (after borrowing)
• 5 - 1 = 4
• Answer: 405

Vedic (left-to-right): 542 - 137

• 500 - 100 = 400
• 40 - 30 = 10 → 410
• But wait, 2 - 7 needs borrowing
• 12 - 7 = 5
• Adjust: 410 - 10 + 5 = 405

With practice, very natural!