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Borrowing (Regrouping)

The Hook

Knocking on the neighbor's door.

What is it?

Taking a value of 10 from the next highest place value when the top digit is too small to subtract from.

Time Travel (History)

Also called 'Decomposition' in modern math teaching.

Cheat Code

Slash the neighbor, drop it by 1, give yourself a 10.

Practice This Now!

The Field Guide

In Plain English: Imagine trying to pay $8 but you only have a $10 bill. You can't give 8 singles. You have to 'break' the ten into ten ones first. That is borrowing.

In The Real World: Making change at a cash register.

How To Do It

  1. Start at the right column.
  2. If Top < Bottom, look left.
  3. Cross out the neighbor, subtract 1 from it.
  4. Add 10 to your current Top number.
  5. Subtract normally.
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Booby Trap!

Subtracting UP! In 52 - 38, students often say 8-2=6. Wrong! You must borrow.

Real World Challenge
"You need 35 wood to build a chest. You have 52. How much extra do you have?"
The Logic: 52 - 35. You can't do 2-5. Borrow from 50. 12-5=7. 4-3=1. Answer: 17.

Training Drills

The Setup
4 12 5 2 - 3 8 ------ 1 4
Borrow 10 from 50.