Rounding is a genuinely useful real-world skill (estimating costs, quick mental maths checks), and the core rule is simple once explained clearly — most confusion comes from one specific sticking point.
The core rule
Look at the digit immediately to the right of the place you're rounding to. If it's 0-4, round down (the digit you're rounding stays the same). If it's 5-9, round up (the digit increases by one). Everything after that digit becomes zero.
Rounding to the nearest 10
47 → look at the units digit (7) → 5 or above, round up → 50. 43 → units digit (3) → below 5, round down → 40.
Rounding to the nearest 100
Same principle, but now look at the tens digit. 350 → tens digit is 5 → round up → 400. 340 → tens digit is 4 → round down → 300.
The sticking point: exactly 5
The standard rule taught in UK primary schools is that exactly 5 always rounds up — 45 rounds to 50, not down to 40. This is a convention, not a mathematical inevitability, which is exactly why it needs to be explicitly taught and remembered rather than "worked out" logically each time.
Why rounding actually matters beyond the test
Rounding underpins estimation — a genuinely useful real-world skill for quickly checking whether a calculated answer looks roughly right, or for mental maths while shopping ("that's about £40 all together"). It's one of the primary maths topics with the most obvious everyday application.
A quick way to practise at home
Round prices while shopping together, or round distances on a car journey — real numbers in context build genuine fluency far more effectively than abstract worksheet numbers alone, and it demonstrates exactly why the skill is useful in the first place.
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