Line up the points, then pad the gaps
The Short Answer
Decimal questions in the 11+ are mostly ordinary arithmetic that has gone wrong at the setting-out stage. Line the decimal points up underneath each other, fill the empty places with zeros so every number has the same length, and then add or subtract exactly as with whole numbers. The point in the answer goes directly below the points above it.
What goes wrong with decimals
Not the arithmetic. The setting-out.
A child who can confidently add 70 and 35 will write 0.7 + 0.35 in a line, align the last digits out of habit, and answer 0.42.
Nothing is wrong with their addition. The columns were wrong before they started.
Line up the points, then pad the gaps
Two steps, and they take about three seconds.
Line the decimal points up underneath each other. Not the last digits — the points.
Fill the empty places with zeros so every number is the same length.
0.70
- 0.35
1.05
Writing 0.7 as 0.70 changes nothing at all. The hundredths column simply holds nothing. What it gives you is a sum with no ambiguity in it, and that is the whole trick.
Subtraction with a whole number
Multiplying: take the point out and put it back
Do the sum with whole numbers, then restore the point.
2.5 × 4. Multiply 25 × 4 = 100. One digit was moved to turn 2.5 into 25, so move one back: 10.
The check is sensibleness. Two and a half fours ought to be about ten, and it is.
Multiplying by ten, a hundred, a thousand
The digits move. The point stays put.
That sounds like a quibble and it is not. Children who picture the point sliding along lose track of it in longer questions, because they end up moving both.
0.04 × 1000 — every digit shifts three places left, giving 40.
Where do pupils lose marks?
Aligning the last digits instead of the points.
Forgetting the point after a whole number, so 12 lines up against 3.
Dropping the point out of the answer entirely after a correct calculation.
Not checking sensibleness — an answer ten times too big or too small is usually obvious if you look at it for a second.
Try it yourself
Set every one of these out vertically, with the points lined up, before calculating.
- What is 0.7 + 0.35?
- What is 12 − 3.6?
- What is 2.5 × 4?
- What is 0.04 × 1000?
- £20 − £13.45. What is the change?
- 1.05. Written as 0.70 + 0.35, this is an ordinary sum. Lining up the last digits instead gives 0.42, which is the commonest wrong answer here.
- 8.4. Write 12 as 12.0 first. A whole number always has a decimal point after it, even when nobody writes one.
- 10. Two and a half fours. Or: 25 × 4 = 100, and since one digit was moved, move it back — 10.
- 40. Each digit moves three places to the left. The digits move; the point stays where it is.
- £6.55. Money is decimals with a fixed two places, which is why it is such good practice — the setting-out is identical and the answer has to make sense.
How much practice does this type need at home?
Shopping does most of the work. Adding two prices in your head, and working out the change from twenty pounds, is decimal arithmetic with a fixed two places and a real answer at the end.
For written practice, the useful instruction is not "do these sums" but "set these out with the points lined up, then do them." The marks on this topic live in the first of those two steps.
Free: a Maths workbook
Questions across the Maths question types, with the method printed at the top and full answers at the back. One workbook for the whole strand, not a sheet per question type.
Frequently Asked Questions
Why does my child get decimal addition wrong when they can add whole numbers?
Almost always because they lined up the last digits instead of the points. Adding 0.7 and 0.35 by right-aligning gives 0.42, which is not close. Lining up the points and padding 0.7 to 0.70 turns it back into a sum they can already do. The arithmetic was never the problem; the setting-out was.
Is padding with zeros allowed?
Yes, and it is worth doing every time. Writing 3.5 as 3.50 does not change its value — the hundredths column simply holds nothing. What it does is give every number the same number of columns, which removes the ambiguity that causes the error. It is the cheapest habit on this topic.
How do you multiply decimals without a calculator?
Take the point out, multiply as whole numbers, and put it back. For 2.5 × 4, do 25 × 4 = 100; one digit was moved to get from 2.5 to 25, so move one back, giving 10. The check is whether the answer is sensible: two and a half fours should be about ten, and it is.
Does the decimal point move when multiplying by ten?
The digits move; the point stays. It sounds like a quibble and it is not — children who believe the point moves lose track of it in longer questions. Multiplying 0.04 by a thousand moves every digit three places left, giving 40. Same rule, same direction, every time.
Sources
- GL Assessment — 11+ familiarisation materials and question type descriptions Published 2025.
- Clever Clogs Academy — our own Year 4 and Year 5 lesson records, Winslow Published September 2025 to July 2026.
We are not affiliated with, endorsed by or connected to GL Assessment or Buckinghamshire Council. Test arrangements change; always check the council's own pages for the current year's dates.
We Teach This Method Every Week in Winslow
Groups of no more than six pupils with two qualified teachers, in person or online. Come and see a session before you decide.