Three-digit adding and taking away · Usually met around P2
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
Go from 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 way: 734 − 258 → 734 − 200 = 534, 534 − 50 = 484, 484 − 8 = 476. Near a whole hundred, you can round and then fix it (compensation). 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 use columns, starting from the ones and carrying or borrowing.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
602 + 209
Show the answer and working
Answer: 602 + 209 = 811
602 + 209: left to right, add one place at a time: hundreds 602 + 200 = 802, ones 802 + 9 = 811
Example 2
605 − 255
Show the answer and working
Answer: 605 − 255 = 350
605 − 255: left to right, take away one place at a time: hundreds 605 − 200 = 405, tens 405 − 50 = 355, ones 355 − 5 = 350
Example 3
796 + 163
Show the answer and working
Answer: 796 + 163 = 959
796 + 163: left to right, add one place at a time: hundreds 796 + 100 = 896, tens 896 + 60 = 956, ones 956 + 3 = 959
Practise it in the game →Three-digit adding and taking away · Free to start, unlimited questions, no download