Adding and subtracting decimal numbers using column method with aligned decimal points.
Where your child meets this in real life: Adding up prices, calculating change with pounds and pence, or totalling measurements
SEAGReady breaks add and subtract decimals into 3 steps, taught in order so each skill builds on the last.
Add and subtract decimal numbers with the same number of decimal places without requiring carrying or borrowing
Add and subtract decimal numbers with the same number of decimal places when carrying or borrowing is required
Add and subtract decimal numbers with different numbers of decimal places by matching place values through zeros
Three free sample questions from our add and subtract decimals course. Every question comes with a full explanation, and hints that guide without giving the answer away.
Ciara bought a ruler for £1.24 and an eraser for £0.53 at the school shop. How much did she spend altogether?
Answer: A. £1.77
Line up the decimal points: 1.24 + 0.53 ------ Hundredths: 4 + 3 = 7 Tenths: 2 + 5 = 7 Ones: 1 + 0 = 1 Answer: £1.77
Stuck? Start here: Line up the decimal points so each column is in the right place.
Sophie walked 3.8 km in the morning and 1.6 km in the afternoon. How far did she walk altogether?
Answer: A. 5.4 km
Line up the decimal points: 3.8 + 1.6 ---- Tenths: 8 + 6 = 14 tenths = 1 whole and 4 tenths Write 4 in tenths, carry 1 to ones Ones: 3 + 1 + 1 = 5 Answer: 5.4 km
Stuck? Start here: When digits add to more than 9, you need to carry.
Niamh has £5 pocket money. She buys a magazine for £2.35. How much money does she have left?
Answer: A. £2.65
Write £5 as £5.00: 5.00 - 2.35 ------ Hundredths: 0 - 5 needs borrowing. Borrow from tenths. But 0 tenths needs to borrow from ones first. 5 becomes 4, 0 tenths becomes 10 tenths. 10 tenths becomes 9 tenths, 0 hundredths becomes 10 hundredths. 10 - 5 = 5 (hundredths) 9 - 3 = 6 (tenths) 4 - 2 = 2 (ones) Answer: £2.65
Stuck? Start here: Write £5 as £5.00 so both numbers have the same number of decimal places.
This is the exact interactive worked example your child sees in SEAGReady. Step through it and watch the method build up.
Aoife bought a notebook for £2.35 and a pen for £1.42 at the school shop.
How much did she spend altogether?
2.35 + 1.42
Step 1 of 5
Aoife bought a notebook for £2.35 and a pen for £1.42 at the school shop.
How much did she spend altogether?
Aoife spent £3.77 altogether.
The key insight: Adding decimals works just like whole numbers - just keep those decimal points lined up!
Watch out: 2.35 + 1.42 = 377 (forgetting the decimal point). The decimal point in the answer must line up with the decimal points above it.
These are the misconceptions we see most often in add and subtract decimals, including the ones our practice questions are specifically designed to catch.
Struggling with add and subtract decimals? The real gap is often in one of these earlier topics.
SEAGReady finds the exact step where your child gets stuck, teaches it with worked examples like the one above, and brings it back for review so it sticks.