Order of operations and brackets · Usually met around P3
Adding and taking away three numbers
Left to right, one step at a time.
How to do it
Method
Left to right, one step at a time
1250 + 368 − 475 = 1618 − 475 = 1143
Another way
Take away the sum
2000 − 356 − 644 = 2000 − 1000 = 1000
In full
With only + and −, work from left to right, one step at a time: 1250 + 368 − 475 → 1250 + 368 = 1618, then 1618 − 475 = 1143. Each step can be done in columns, places lined up, carrying and exchanging as needed. Another way: taking away two numbers in a row is taking away their sum: 2000 − 356 − 644 = 2000 − 1000 = 1000 — quick when they make a whole hundred or thousand. To check, work backwards: 1143 + 475 − 368 = 1250.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
2046 + 614 − 408 = □ − 408 = □
Fill in each box
Show the answer and working
Answer: 2660，2252
First 2046 + 614 = 2660, then 2660 − 408 = 2252.
Example 2
2326 − 178 − 730 = □
Show the answer and working
Answer: 1418
2326 − 178 = 2148, 2148 − 730 = 1418.
Example 3
614 + 342 − 183 = 773
True or false?
Show the answer and working
Answer: True
614 + 342 − 183 = 773: watch the carrying and exchanging in each step.
Practise it in the game →Order of operations and brackets · Free to start, unlimited questions, no download