Primary 1 Addition and Subtraction

Keywords

Connect each word to a story, objects or a drawing before asking your child to use a symbol.

Add / plus

Join amounts or increase an amount. The symbol is +.

Subtract / minus

Take away or find a difference. The symbol is −.

Sum / total

The amount altogether after adding.

Difference

How much more one amount is than another.

Part and whole

Two parts can join to make one whole.

Number bond

A drawing that shows a whole and its parts.

Number line

A line of numbers used to show jumps forward or backward.

Inverse facts

Addition and subtraction facts that use the same parts and whole.

Regrouping

Trade ten ones for one ten, or one ten for ten ones, without changing the amount.

Tens / ones

The places used to line up two-digit numbers in vertical working.

Question clues: “Altogether” can mean find the whole. “Left” can mean find a remaining part. “How many more?” asks for a difference. Read the whole story before choosing an operation.

What addition and subtraction mean

Addition joins or increases. Subtraction takes away, finds a missing part or compares two amounts. A number bond shows the relationship. On a number line, count forwards to add and count backwards to subtract.

Important: Count the spaces moved on a number line, not the starting dot. The starting point is already counted.

Common mistake: Starting at 3 and calling it “one” during a +4 jump. Point to 3, then count the next four spaces: 4, 5, 6, 7.

Ask: “Where do we start? Are we moving forward or backward? Where do we land?”

How addition and subtraction are related

Four balloons stay tied and three float away. There were seven balloons at first. The picture gives one fact family: 3 + 4 = 7, 4 + 3 = 7, 7 − 3 = 4 and 7 − 4 = 3.

Important: Switching the two parts in addition keeps the total. In subtraction, begin with the whole and remove a part.

Common mistake: Writing 3 − 7 because those numbers appear in the story. The whole is 7, so 7 must come first when taking 3 away.

Ask: “What was the whole at first? Which part flew away? Which part stayed?”

Add and subtract within 10

Use fingers, counters, a number bond or a short number line. Work within 10 until your child can explain which amount is the whole and which amounts are parts.

Important: Encourage the child to start from the larger amount and count on for addition, rather than recounting every counter.

Common mistake: Counting the first group again when adding. Keep six counters still, then count on “seven, eight, nine” for the three new counters.

Ask: “What amount do we already have? How many more are joining or leaving?”

Add and subtract within 20

Use the split method to work with ten and ones. The branches beneath each equation show which number is split. For addition across ten, split the amount being added so the first step makes ten.

Important: For 8 + 5, splitting 5 into 2 and 3 helps make ten. For 13 − 5, splitting 13 into 10 and 3 lets your child take 5 from the ten, then add the 3 ones.

Common mistake: Saying 8 + 5 = 12 after making ten, because the three leftover ones are lost. Keep the parts visible: 8 + 2 + 3 = 13.

Ask: “Which number should we split? Can we make ten for addition, or subtract from ten and then join the ones?”

Add and subtract within 100

Line up tens under tens and ones under ones. Build the numbers with base-ten blocks first. If the ones make ten or there are not enough ones to subtract, regroup between the tens and ones places.

Important: Regrouping changes the way a number is shown, not its value. 52 is still 52 when shown as 4 tens and 12 ones. Use the printable vertical working sheet to keep each digit in its place. A total of 100 needs a 1 in the hundreds place.

Common mistake: In 52 − 27, trying 7 − 2 in the ones column, or forgetting that the 5 tens became 4 tens after regrouping. Build 52 as blocks and regroup one ten before calculating.

Ask: “What do the ones make? Do we need to regroup? How many tens are left after regrouping?”

How to help at home

Ask your child to tell the story with objects first, then draw a number bond, number line or bar model. Move to vertical working after they can explain the tens and ones. Let them reveal each practice answer only after trying it.

Printables

Use the blank hundreds, tens and ones columns for addition and subtraction working.