Stage 2 · Add & subtract strategies
Three-digit + and −
Left to right, one place at a time.
How to do it
Method
Left to right, one place at a time
248 + 385 = 548 + 85 = 628 + 5 = 633
Another way
Columns
From the ones: 8 + 5 = 13, write 3, carry 1; 4 + 8 + 1 = 13, write 3, carry 1; 2 + 3 + 1 = 6 → 633
In full
Left to right, one place at a time: 456 + 278 → hundreds first, 456 + 200 = 656, then tens, 656 + 70 = 726, then ones, 726 + 8 = 734. Subtraction works the same: 734 − 258 → 734 − 200 = 534, 534 − 50 = 484, 484 − 8 = 476. Near a whole hundred you can compensate: adding 298 is adding 300 and taking 2 off (456 + 298 → 756 − 2 = 754); taking away 298 is taking away 300 and giving 2 back. Or work in columns from the ones, carrying or borrowing; the answer is the same.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
481 + 120
Show the answer and working
Answer: 481 + 120 = 601
481 + 120: left to right, add one place at a time: hundreds 481 + 100 = 581, tens 581 + 20 = 601
Example 2
326 − 245
Show the answer and working
Answer: 326 − 245 = 81
326 − 245: left to right, take away one place at a time: hundreds 326 − 200 = 126, tens 126 − 40 = 86, ones 86 − 5 = 81
Example 3
132 + 796
Show the answer and working
Answer: 132 + 796 = 928
132 + 796: left to right, add one place at a time: hundreds 132 + 700 = 832, tens 832 + 90 = 922, ones 922 + 6 = 928
Example 4
577 − 129
Show the answer and working
Answer: 577 − 129 = 448
577 − 129: left to right, take away one place at a time: hundreds 577 − 100 = 477, tens 477 − 20 = 457, ones 457 − 9 = 448
Practise three-digit + and − in the game →Stage 2 · Add & subtract strategies · Free to start, unlimited questions, no download