Learn column addition and subtraction with up to 4 digits, exchanging, estimating and checking, by helping Tock the owl load airships at Sky Harbour.
Year 4 maths · 1
Year 4 maths · 1
Year 4 maths · 1
Year 4 maths · 1
Year 4 maths · 2
Year 4 maths · 2
Year 4 maths · 3
What the chapters cover in the national curriculum in England:
Column addition and subtraction is the focus of Sky Harbour Sums, an interactive maths game for children aged 7–10 that teaches the Year 4 written methods for adding and subtracting numbers with up to 4 digits. It follows the national curriculum in England for Key Stage 2.
Players help Tock the owl harbour master count crates on and off airships. Place value counters sit next to each written calculation, so children see ten ones being exchanged for one ten, or a ten being broken into ten ones, before they write the digits. Guided examples talk them through one column at a time; then they solve sums on their own, typing each answer digit and tapping to exchange.
Later chapters cover estimating by rounding, checking with the inverse operation, and two-step word problems where the child decides whether to add or subtract at each step and why.
When the top digit in a column is smaller than the bottom digit, you exchange one from the column to the left. You cross out that digit, write one less, and the column you are working on gets ten more, so 2 − 7 becomes 12 − 7.
Carrying means exchanging ten in one column for one in the next column to the left. If the ones make 13, you write 3 in the ones column and a small 1 below the line in the tens column, then add it in.
You exchange from the nearest column that has something to give and pass it along. One thousand becomes ten hundreds, one hundred becomes ten tens, and one ten becomes ten ones, so the zeros become 9s and the ones become 15.
Children in England meet column methods in Year 3 and use them with up to 4-digit numbers in Year 4, usually at ages 8 to 9. This game suits children aged 7 to 10, including those who need a refresher.
The game has seven chapters, an optional place value warm-up and a 10-question final challenge, and takes about 75 minutes to play through. Children can start any chapter from the map and come back to it later.
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