Arithmetic precision facts for kids
The precision of a number tells us how many digits are used to show its value. Think of it as how detailed or exact a number is.
In science, precision often means the total number of digits in a number. These are called significant figures or significant digits. For example, the number 12.345 has five significant figures.
Sometimes, precision refers to the number of digits after the decimal point. These are called decimal places. This is very useful in areas like finance (money) and engineering, where those specific digits matter a lot. For instance, money is usually shown with two decimal places (like $12.34).
Precision also helps us know where to round a number that isn't exact. When you round a number, you're making it fit a certain level of precision. For example, if you're dealing with money, you often round to two decimal places.
Understanding Precision
Let's look at the number 12.345. We can show it with different levels of precision. If we don't have enough space or need to simplify, we round the number. The table below shows how 12.345 changes when rounded to different significant figures or decimal places. We're using a common rounding method called "round-to-even."
| Precision | Rounded to significant digits | Rounded to decimal places |
|---|---|---|
| Five | 12.345 | 12.34500 |
| Four | 12.34 | 12.3450 |
| Three | 12.3 | 12.345 |
| Two | 12 | 12.34 |
| One | 1 × 101 | 12.3 |
It's important not to show a number with more digits than you can actually measure. For example, if a scale measures to the nearest gram and shows 12.345 kg, it would be wrong to write "12.34500 kg." Adding extra zeros ("00") would create false precision, making it seem more exact than it really is.
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See also
In Spanish: Cifras significativas para niños
