Operations with large numbers
Adding, subtracting, multiplying and dividing large numbers, estimating to check. Commutative, associative and distributive: shortcuts for mental maths. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
Large numbers
- Group digits in threes: 12 345 678.
- Estimate by rounding first, then calculate in columns.
- Use the correct order of operations (BODMAS).
Properties of operations
| Property | What it says | Example |
|---|---|---|
| commutative | order does not matter for + and × | 3 + 5 = 5 + 3; 4 × 7 = 7 × 4 |
| associative | grouping does not matter for + and × | (2 + 3) + 4 = 2 + (3 + 4) |
| distributive | spread the multiplication over a sum | 6 × 14 = 6 × 10 + 6 × 4 = 84 |
Subtraction and division are not commutative: 8 − 3 ≠ 3 − 8.
- Any number × 1 = the same number; any number × 0 = 0.
- Any number + 0 = the same number.
Remember this and test yourself
- Group digits in threes.
- Commutative: 3 + 5 = 5 + 3 (also ×).
- Estimate first.
- Associative: brackets can move for + and ×.
- Calculate in columns.
- Distributive: 6 × 14 = 6 × 10 + 6 × 4.
Write these points in your book. Read them again the night before the test.
Three-three-three: read big numbers in groups.
Important words
First say the answer yourself, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: Operations with large numbers- Let your child work the examples on paper and explain them to you.
- The ticks (“I know this”) are saved on this device only. We never ask for names or emails.
Follows CAPS for Grade 7 Mathematics. Always check your teacher’s notes and textbook too.