Making a whole using decimals for 11+ maths
21 October 2026
Making a whole using decimals
Understanding how to make a whole number by adding decimals is a key skill for the 11+ maths exam. This helps children see how parts fit together to make one complete number.
Why this matters
Questions about decimals often appear in the 11+ test. Children need to recognise which decimals can be combined to make 1, and be confident in their calculations.
Key insight: Adding decimals to make a whole
Adding decimals is just like adding whole numbers, but you must keep the decimal points lined up. Encourage your child to check their answer always adds up to exactly 1.
Worked example
Let's look at how to make 1 using several decimals.
Start with 0.4
Add 0.3: 0.4 + 0.3 = 0.7
Add 0.2: 0.7 + 0.2 = 0.9
Add 0.1: 0.9 + 0.1 = 1.0
So, 0.4 + 0.3 + 0.2 + 0.1 = 1.0
Tips for parents
Give your child practice with different combinations of decimals. Use coins or draw diagrams to show how smaller parts make a whole. This builds confidence and accuracy.
Building strong foundations
Mastering decimal addition helps your child with fractions, percentages, and more advanced maths. Practise regularly and break each step down to keep learning stress-free.
