Idea 8of 23Builds onPut a number in for the letter
Multiply first, then add
In 4 + 2n, which part do you work out first?
Today you'll discover
- why 2n is one number
- what goes wrong left to right
- how the picture shows the order
Think first4 loose cubes and two bags of n
If n = 6, what is 4 + 2n?
Decide first, then press Next. Find the bags first, then the loose cubes.
4 loose squares and two bags marked n, with 4 + 2n under them. Then the bags open to show 6 each, and the working 4 + 2 × 6 = 4 + 12 = 16. The last step shows 7 loose cubes and four bags of n: 7 + 4n.
See the whole ideathe big idea and the key word, in one place
The big idea
In an expression, multiply first, then add or subtract.
Compare them4 + 2n with n = 6 is 4 + 12 = 16. Working left to right gives 6 × 6 = 36, as if there were 6 bags.
For example6 + 3n with n = 2: 3 × 2 = 6 first, then 6 + 6 = 12.
Key word
- order of operations
- the order to work out a calculation: multiply and divide before you add and subtract
Ready to use it?
- Evaluate expressions like 4 + 2n, multiplying first.