Mass and weight problems for 11+ maths: a parent's guide
21 October 2026
Understanding mass and weight
Mass and weight are often confused, but they are not the same. Mass is the amount of matter in an object and is measured in kilograms (kg) or grams (g). Weight is the force of gravity acting on that mass and is measured in newtons (N).
Key insight: Mass stays the same anywhere, but weight depends on gravity
On Earth, weight is calculated by multiplying mass by the acceleration due to gravity. For the 11+ exams, children need to understand that mass does not change, but weight can change if gravity changes, for example, on the Moon.
Common mass and weight problems in 11+
Questions may ask children to add or subtract masses, convert between grams and kilograms, or calculate weight using gravity. Some problems involve real-life contexts, like comparing the mass of objects or finding the total weight of several items.
Worked example
A bag weighs 5 kg and a box weighs 3 kg. What is their total mass?
First, write down the mass of each item: bag = 5 kg, box = 3 kg.
Add the two masses together: 5 kg + 3 kg = 8 kg.
The total mass is 8 kg.
Tips for supporting your child
Encourage your child to read each question carefully and check the units. Remind them to convert grams to kilograms or vice versa when needed. Practise adding and subtracting masses and, if a question asks for weight, use the formula: weight = mass × gravity (usually gravity is given as 10 N/kg or 9.8 N/kg for 11+ questions).
Building confidence with practice
Regular, calm practice with a range of mass and weight problems will help your child feel prepared. Focus on understanding the difference between mass and weight, using clear steps for each calculation, and always checking the answer makes sense for the context of the problem.
