Thumbs up if you think the same rule still works; thumbs sideways if you think we need a new rule. Then three hands up for the reasoning.

Watch as we work four decimal subtractions on the column-subtraction tool. Notice how the same line-up-the-points rule you already know from adding decimals still holds, but instead of carrying we now decompose — we break a unit down into ten of the smaller place value next to it.

Example 1: 4.5 − 1.75 = 2.75

The 4.5 becomes 4.50 so the hundredths column has something to subtract from. Then we regroup one tenth into ten hundredths to take 5 away.

Example 2: 0.6 − 0.27 = 0.33

A lonely tenth on top. The trailing zero on 0.60 makes the hundredths column visible — then we regroup just like before.

Example 3: 1.0 − 0.85 = 0.15 (the chain)

The whole one breaks down in a chain. It splits into ten tenths, one of which then splits into ten hundredths.

Example 4: 5.005 − 0.999 = 4.006

Thousandths now. The same chain reaches one column further to the right — every column needs to regroup.

Now let's work the same kind of subtraction together. Today we try: 3.2 − 1.45. We enter the top number and the bottom number on the column-subtraction tool, then we step through each column from the right — the smallest place first, regrouping when the top digit is too small.