Close enough, on purpose
Why Do We Round Numbers?
Rounding trades a little accuracy for a number you can actually hold in your head.
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Step 1 of 5
Exact numbers are often more than you need.
If a stadium holds 3,847 people, the 47 rarely matters. Saying about four thousand carries the useful part and drops the rest.
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Step 2 of 5
Rounding asks which landmark is nearer.
Put the number on a line between the two nearest round numbers and see which one it sits closer to. That is the whole method.
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Step 3 of 5
Exactly halfway needs an agreed rule.
A number like 3,500 sits the same distance from both. There is no right answer, so we simply agree to round halves upward.
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Step 4 of 5
How much you round is your choice.
The same number can round to 3,850 or 3,800 or 4,000. Each step throws away more detail and buys you a simpler number.
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Step 5 of 5
Rounding too early spoils the answer.
Rounding each number before adding lets every small error pile up. Work with exact figures and round only the final result.
Round 2.4 and 2.4 up to 3 each and their total jumps from 4.8 to 6 — a 25% error created purely by rounding too early.
The short version
Rounding trades a little accuracy for a number that is far easier to think with, and should be done at the end, not the start.
Try it yourself
Add up a shopping basket by rounding each price to the nearest pound, then check the real total. You will usually be within a pound or two.
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