Three-digit adding and taking away · Usually met around P2
Three-digit adding and taking away, no carrying
Hundreds, tens and ones, each with its own.
How to do it
Method
Hundreds, tens and ones, each with its own
352 + 146: 4 hundreds, 9 tens, 8 ones → 498
Another way
Left to right
352 + 100 + 40 + 6 = 498
In full
A three-digit number is made of hundreds, tens and ones: 352 is 3 hundreds, 5 tens and 2 ones. Adding whole hundreds changes only the hundreds: 352 + 200 = 552; taking them away too: 552 − 200 = 352. To add two three-digit numbers when no place makes 10, put hundreds with hundreds, tens with tens and ones with ones: 352 + 146, 3 + 1 = 4 hundreds, 5 + 4 = 9 tens, 2 + 6 = 8 ones, so 498. Taking away when every place is big enough works place by place too: 498 − 146 = 352. Or go left to right a step at a time: 352 + 100 = 452, 452 + 40 = 492, 492 + 6 = 498. Check a taking away by adding: 352 + 146 = 498.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
300 + 500 = □
Show the answer and working
Answer: 800
3 hundreds and 5 hundreds make 8 hundreds, which is 800.
Example 2
559 − 223 = □
Show the answer and working
Answer: 336
Every place is big enough, so take away hundreds, tens and ones in turn: 559 − 223 = 336. Check: 336 + 223 = 559.
Example 3
270 + 723 = 893
True or false?
Show the answer and working
Answer: False
Hundreds, tens and ones each with its own: 270 + 723 = 993.
Practise it in the game →Three-digit adding and taking away · Free to start, unlimited questions, no download