Adding in columns
347
+215
562
Addition and Subtraction
In Year 3, children add and subtract numbers with up to three digits, both in their heads and with the formal written column method. They learn to line digits up by place value and to carry or exchange across the hundreds, tens and ones, and to estimate an answer first before checking it with the inverse operation. None of it is as daunting as it sounds once the columns line up.
Practise Addition and Subtraction
Have a guess, even if you're not sure. Get one wrong and we'll show you why, so every miss is a chance to learn.
Timed practice
The same practice, just with a gentle clock. Pick a length and see how many you can answer.
Good to know
The column method
Here are two sums set out in columns, like the ones you will practise: one that carries and one that exchanges.
Taking away in columns
482
-156
326
For grown-ups
Underneath all of this sits place value: knowing that the 5 in 562 means five hundred is what makes carrying and exchanging make sense rather than feel like a rule to memorise. Mental strategies grow alongside the written method, from number bonds that bridge ten to complements that make 100, so children can reach for whichever is quicker. Estimating first and then checking with the inverse builds the habit of asking whether an answer is reasonable, which is the foundation for column work with larger numbers, money and decimals in the years ahead.
What is in this topic
- Mental addition and subtraction
- Column addition and subtraction up to three digits
- Number bonds that bridge ten
- Complements to 100
- Estimating and checking with the inverse operation
How to help at home
The column method is all about lining digits up and working one column at a time, so a few small habits make it click.
- Line up the digits by place value: ones under ones, tens under tens, hundreds under hundreds. Squared paper, or a quickly drawn three-box grid, stops a 3 drifting under a 30.
- Always start in the ones column on the right and move left, so any carry or exchange happens before you reach the next column.
- Say the carry out loud: "7 plus 5 is 12, write the 2, carry the 1." Writing that small 1 at the top of the tens column and remembering to add it is the step most often missed.
- Estimate first, then check with the inverse. For 347 + 215, round to 350 + 200 to expect about 550, then check the answer 562 by subtracting: 562 take away 215 should give 347.
Where children get stuck
The most common slip in addition is forgetting the carry. A child works out 7 + 5 = 12, writes 12 in the ones column, and pushes everything out of line, or writes only the 2 and forgets to add the carried 1 to the tens. The fix is to treat "write the 2, carry the 1" as one move that always happens together, and to write the small 1 in the tens column straight away so it cannot be forgotten.
In subtraction, the classic error is taking the smaller digit from the larger whichever way round they sit, so for 482 - 156 a child does 6 - 2 in the ones and gets the wrong answer. The correct move is to exchange: one ten from the tens column becomes ten ones, so the 2 becomes 12, do 12 - 6 = 6, and remember the 8 tens has dropped to 7. Pulling out base-ten blocks or coins and physically swapping one ten for ten ones makes exchanging feel real rather than a rule to memorise.