Mental arithmetic
- Look for a near number.
- Compensate after changing it.
- Check the adjustment.
Answer: 48 + 25 = 50 + 25 - 2 = 73
🔢 Number
Mental arithmetic
Learn mental arithmetic with a GCSE-style explanation, help guide, worked example, practice question and flashcards.
Global XP
Level 10 / 100 XP
1. Explanation
Key idea
- Mental arithmetic is part of number and appears often in KS3–GCSE maths.
- Mental arithmetic uses efficient strategies such as partitioning and compensation.
- Use the worked model, help guide, interactive question and flashcards to practise mental arithmetic until the steps feel automatic.
Real-life examples
- Shopping, sport, travel, science, design and everyday decisions all use this skill.
2. Visual
Mental arithmetic learning map
Understand the key idea → follow the help guide → practise a question → check your method → build speed with flashcards.
3. Help guide
How to tackle Mental arithmetic
- Learn the rule: Mental arithmetic uses efficient strategies such as partitioning and compensation.
- Worked model: Look for a near number. Compensate after changing it. Check the adjustment.
- Try the interactive question without looking at the answer first.
- Use the flashcards to test the rule, the method and a common check.
4. Worked examples
Step-by-step working
5. Interactive questions
Try it yourself
Calculate 99 + 36 mentally.
6. Flashcards
Master quick recall
Flip each card, then choose whether you know it or need more practice.
0 mastered
FrontRule for Mental arithmetic
BackMental arithmetic uses efficient strategies such as partitioning and compensation.
FrontExample answer: Calculate 99 + 36 mentally.
Back99 + 36 = 100 + 36 - 1 = 135.
FrontCommon check for Mental arithmetic
BackCheck units/notation, compare with an estimate, and make sure the answer matches the question.
7. Finish
Complete this topic
When you have read the examples, tried the question and reviewed flashcards, claim your topic completion XP.