11+ Maths: Making a Whole Using Decimals
21 October 2026
Why making a whole with decimals matters
Many 11+ maths questions test if children can add or subtract decimals to make exactly one whole. This skill helps with mental maths and builds confidence for trickier problems later on.
Key insight: Understanding how decimals add up to a whole is a foundation for later topics like percentages and fractions.
How to approach these questions
Start by looking for decimal numbers that add up to 1.0. Remind your child to line up the decimal points and add carefully. If subtracting, check what needs to be added to reach one whole.
Worked example
Let's add 0.25 + 0.5 + 0.25
First, add 0.25 + 0.5. This equals 0.75.
Next, add 0.75 + 0.25. This equals 1.0.
The answer is 1.0. Always check each step to make sure the total is exactly one whole.
Checking your answer
After adding or subtracting, encourage your child to double-check by adding the numbers again in a different order or using subtraction to see what is needed to reach 1.0.
Tips for parents
Practise with different decimal combinations to help your child spot pairs or groups that make a whole. Use real-life examples, like money, to make practice more engaging.
