SuBtRaCtIoN!!! subtraction, SUBTRACTION!!!

We worked on THREE subtraction methods today!!

Method ONE:  Trade-First Method

This method is similar to the method for subtracting that most adults were taught when they were in school.
Here is the Trade-First Method for subtracting 3 digit numbers

• Look at the digits in the 1s place.  If subtracting these digits gives a NEGATIVE number, TRADE 1 ten for 10 ones.
• Look at the digits in the 10s place.  If subtracting these digits gives a NEGATIVE number TRADE 1 hundred for 10 tens.
• Subtract in each column   

 

Method TWO:  Partial-Difference Method
Subtract from left to right, one column at a time.
In some cases, the larger number is on the bottom and the smaller number is on the top.  When you subtract these numbers, the difference will be a negative number







Method THREE:  LEFT -to- RIGHT Method

• Start at the left, subtract column-by-column