There are a couple of useful mental methods for subtraction.

# Mental Methods

Example:

## Method 1 – Count On

Count on from 56 until you reach 93. This can be done in several ways e.g.

## Method 2 – Break Up the Numbers Being Subtracted

e.g. subtract 50, then subtract 6

# Written Methods

We use the decomposition method. The numbers must be written with the units, tens and hundreds correctly in line.

## Step 1

Subtract the units. Here, we cannot have 0 – 6 so 10 is added to the zero. 10 – 6 = 4.

## Step 2

Subtract the tens. In this case, as 10 was added to the units in the top row, it must now be subtracted from the tens so the 9(0) becomes 8(0). 8 – 8 = 0.

## Step 3

Subtract the hundreds. In this case it is simple. 5 – 3 = 2.

## Step 4

Subtract the thousands.