Turn a recurring decimal such as 0.4545… into an exact fraction using a short algebra trick. It is Higher only, aimed at grade 6. Free questions with answers are on this page. Worked examples show each line before you try the questions.
A recurring decimal such as 0.17˙ or 0.12 is a fraction in disguise. The method is algebra: let x equal the decimal, multiply by 10, 100 or 1000 until the repeating block lines up, subtract, and divide. One repeating digit: ×10. Two repeating digits: ×100. A delay before the repeat (0.53˙) needs two different multiplications so the non-repeating part cancels.
Simplify the fraction. 0.6˙=32, not 96 left unsimplified. The reverse (fraction to recurring decimal) is long division of the numerator by the denominator. A terminating decimal is a fraction whose denominator's primes are only 2 and 5.
Call the decimal x, multiply to shift one full repeating block, subtract so the tail cancels, then simplify. One repeating digit uses ×10; two digits ×100. A non-repeating starter such as 0.36˙ needs both 10x and 100x.
Objectives
Write a one-digit repeat as a fraction over 9.
Write a two-digit repeat as a fraction over 99.
Turn a simple fraction back into a recurring decimal.
Key points
Read dot notation: 0.7˙ means 0.777… and 0.4˙5˙ means 0.454545…
Call the decimal x, multiply by 10, 100 or 1000 to shift one full repeating block, then subtract.
Handle decimals that start with a non-repeating digit, such as 0.23˙.
Simplify the final fraction fully.
Worked examples
Example 1
Convert 0.777... to a fraction in its simplest form.
2 marks
Identify the repeating block: the single digit 7 repeats.
Place the repeating digit over 9: 7/9.
7/9 cannot be simplified further, so the final fraction is 7/9.
Answer: 7/9
Common slips
Slip: Treat 0.777... as 7/10. One repeating digit means a denominator of 9, not 10.
Slip: Write 777/1000. 777/1000 truncates the recurring decimal after three places.
Slip: Round the answer to 0.78. Exact form requires a fraction, not a rounded decimal.
Example 2
Convert 0.121212... to a fraction in its simplest form.
2 marks
Identify the repeating block: the two digits 12 repeat.
Place the block over 99 to get 12/99.
Divide numerator and denominator by their common factor 3 to get 4/33.
Answer: 4/33
Common slips
Slip: Treat the decimal as terminating: 12/100. A two-digit repeating block goes over 99, not 100.
Slip: Place the block over 9 to get 12/9. Two repeating digits require 99 on the bottom.
Slip: Leave 12/99 uncancelled. Always reduce fractions to simplest form.
Example 3
Use algebra to write 0.636363... as a fraction in its simplest form.
3 marks
Let x = 0.636363... Two digits repeat, so multiply by 100: 100x = 63.636363...
Subtract x from 100x. The tails cancel: 99x = 63, so x = 63/99.
Divide top and bottom by 9: 63/99 = 7/11.
Answer: 7/11
Common slips
Slip: Multiply by 10 to get 10x = 6.3636... The block has two digits, so multiply by 100. Multiplying by 10 does not line up the repeats.
Slip: Subtract and write 99x = 63.6 Both lines have the same tail, so it cancels and leaves a whole number: 99x = 63.
Slip: Leave the answer as 63/99 Cancel to simplest form: 63 ÷ 9 = 7 and 99 ÷ 9 = 11.
Questions and answers
GCSE Maths recurring decimals to fractions questions and answers. Try each one, then open the answer. Easy questions come first.
Question 1 Easy2 marks
Convert 0.444... to a fraction in its simplest form.
Show answer
Answer: 4/9
One repeating digit 4 sits over 9.
4/9 cannot be simplified.
M1 — One repeating digit 4 sits over 9.
A1 — 4/9 cannot be simplified.
Question 2 Easy2 marks
Convert 0.222... to a fraction in its simplest form.
Show answer
Answer: 2/9
One repeating digit 2 sits over 9.
2/9 cannot be simplified.
M1 — One repeating digit 2 sits over 9.
A1 — 2/9 cannot be simplified.
Question 3 Medium2 marks
Convert 0.454545... to a fraction in its simplest form.
Show answer
Answer: 5/11
Two-digit repeating block 45 sits over 99.
Divide numerator and denominator by 9: 45/99 = 5/11.
M1 — Two-digit repeating block 45 sits over 99.
A1 — Divide numerator and denominator by 9: 45/99 = 5/11.
Question 4 Medium2 marks
Convert 0.363636... to a fraction in its simplest form.
Show answer
Answer: 4/11
Two-digit repeating block 36 sits over 99.
Divide numerator and denominator by 9: 36/99 = 4/11.
M1 — Two-digit repeating block 36 sits over 99.
A1 — Divide numerator and denominator by 9: 36/99 = 4/11.
Question 5 Hard2 marks
Find the recurring decimal for the fraction 1/3.
Show answer
Answer: 0.3 recurring
Perform division: 1 ÷ 3 = 0.333...
The single digit 3 repeats indefinitely, written as 0.3 recurring.
M1 — Perform division: 1 ÷ 3 = 0.333...
A1 — The single digit 3 repeats indefinitely, written as 0.3 recurring.
Question 6 Hard2 marks
Find the recurring decimal for the fraction 2/9.
Show answer
Answer: 0.2 recurring
Perform division: 2 ÷ 9 = 0.222...
The single digit 2 repeats indefinitely, written as 0.2 recurring.
M1 — Perform division: 2 ÷ 9 = 0.222...
A1 — The single digit 2 repeats indefinitely, written as 0.2 recurring.
Question 7 Exam-style4 marks
Convert 0.545454... to a fraction in its simplest form.
Show answer
Answer: 6/11
Let x = 0.545454... and 100x = 54.545454...
Subtract: 99x = 54, so x = 54/99.
Divide numerator and denominator by 9: 54 ÷ 9 = 6 and 99 ÷ 9 = 11.
The simplified fraction is 6/11.
M1 — Set up subtraction 100x - x = 99x = 54
M1 — Write fraction as 54/99
M1 — Divide top and bottom by 9
A1 — Simplified fraction 6/11
Common mistakes
Most lost marks on this topic are one slip.
Using 10 or 100 as the denominator for a repeating block
Use 9 for one digit and 99 for two
Leaving 45/99 when it still cancels
Divide top and bottom by 9
Rounding a recurring decimal that was asked for as a fraction
Keep the cancelled fraction
Spot the slip
Ada says 0.777... equals 7/10 because she only looks at the first digit. Which fraction is exact?
7/9
7/10
777/1000
Show the slip
7/9 One repeating digit is a fraction with 9 on the bottom.
Exam tips
Be ready to do this without a calculator. Paper 1 is the non-calculator paper.
If the question says “show that”, the result is given. The marks are for the steps that reach it.
The method is the same on AQA-style and Edexcel-style papers.
Write 'Let x=…' and show both multiplied lines — the method marks come from these lines even if you slip at the end.
This is non-calculator. Check your fraction by dividing mentally: 7÷9 starts 0.77…, so 97 looks right.
Printable worksheet
The same questions are in a PDF you can print. Answers start on a later page.