Number Splitting

There are several methods for using number splitting for subtraction. Many of the structured ones are basically setting the stage for the borrowing algorithm. Funny Numbers are a fun way to get students borrowing that also uses multiple representations. JJ’s method is a little more flexible, but just decomposition again.

One structured approach looks like this:

Split the minuend and subtrahend on the hundreds, tens, and ones. As you can’t subtract 7 from 2 and end up with a positive numbers, move ten over. Subtract tens from tens, units from units. Put the two pieces of the difference together.

Some people like to use a chart format.

Another approach is to split the second number.

82 – 37

= 82 – 30 – 7

= 52 – 7

= 45

Amoeba Subtraction

A game from the BBC that probably illustrates decomposition subtraction better than I can.

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