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Adding and subtracting uneven decimals worksheets

The hard decimal questions are the uneven ones: 4.5 plus 12.375, where one number runs to thousandths and the other stops at tenths. These free printable worksheets add and subtract decimals with different numbers of places, so lining up the point is the whole test.

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Adding and subtracting uneven decimals
Adding and subtracting uneven decimals worksheet — Different numbers of places, free printable with answer key

The answer key prints on a separate page.

What's on this sheet

When both numbers have the same places, lining up the point and lining up the right-hand edge look identical — and that is exactly why they hide the rule. Give the two numbers different lengths and the difference bites: 4.5 + 12.375 goes wrong the moment a child lines up the ends instead of the points, because the 5 lands under the 5 of 375 rather than in the tenths where it belongs.

Why this sheet works

Filling the gaps with zeros is the fix and the habit. Writing 4.5 as 4.500 says out loud that four and a half has no hundredths or thousandths, which is true and makes the columns honest; a blank column is where an invented digit or a dropped borrow creeps in. Subtraction is where it shows most — 17.9 − 14.913 needs 17.900 before the borrowing can even start.

How this one works

One question from this sheet, worked through a step at a time.

72.80 − 34.48

612710 72.80 34.48 38.32
  1. 72.80 − 34.48. Line the POINTS up under each other — not the right-hand ends. Right-aligning is what turns 12.5 + 3.75 into a tidy-looking wrong answer.
  2. 0 is too small to take 8 from, so a ten comes across from the left: this column now holds 10. 10 − 8 = 2.
  3. This column gave a ten to the right, so it is now 7, not 8. 7 − 4 = 3.
  4. 2 is too small to take 4 from, so a ten comes across from the left: this column now holds 12. 12 − 4 = 8.
  5. This column gave a ten to the right, so it is now 6, not 7. 6 − 3 = 3.
  6. The point in the answer comes straight down from the ones above it — it was never moved, only lined up. 72.80 − 34.48 = 38.32.

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