Rounding numbers — Mathematics, 7–10 years
Rounding replaces a number with a nearby, simpler number while keeping its size sensible. Mathematics, 7–10 years.
A nearby simpler number
Rounding means choosing the nearest useful number, such as changing 47 to 50 or 43 to 40. We look at the digit just after the place we want to keep: 5 or more moves up, and 4 or less stays down.
Why round?
Exact numbers are important, but they can be awkward when we estimate a cost, a crowd, or a distance quickly. Rounding gives a useful answer without pretending it is exact, so we can check whether a calculation is sensible.
Round 368 to the nearest ten
Keep the tens digit, 6, and inspect the ones digit, 8. Because 8 is at least 5, increase 6 to 7 and replace the ones with 0. So 368 rounds to 370, not 360.
The tempting shortcut
A common mistake is to look at the whole number and choose whichever round number feels close. That can work by luck, but the place being rounded decides which digit to inspect: nearest ten and nearest hundred use different clues.
Quick estimates
A shop total of 19.80 euros is about 20 euros, and 198 people are about 200 people. These estimates help you decide quickly whether you have enough money or whether a reported answer could be far too large.
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