LESSON 2 · Mental Math Shortcuts
Add Up Instead
Subtraction feels harder than addition because borrowing creates mental overhead. The fix: add up from the smaller number. For 1000 - 683, start at 683, add 17 to reach 700, then add 300 to reach 1000. Total added: 317. That is your answer, with no borrowing at all.
Shopkeepers used this counting-up trick for centuries to make change. Pay for a $13.47 item with a $20 bill: count up 53 cents to $14, then $6 to $20. Change: $6.53. Two easy hops beat one hard subtraction.