Plus-minus sign facts for kids
Quick facts for kids ± |
|||
|---|---|---|---|
|
Plus-minus sign
|
|||
|
|||
The plus-minus sign (±) is a special symbol used in many different areas, especially in mathematics and science. It looks like a plus sign (+) on top of a minus sign (-). This symbol usually means "plus or minus," telling you there are two possible values or options.
Contents
What Does the Plus-Minus Sign Mean?
The plus-minus sign (±) has different meanings depending on where you see it. It's a handy way to show two possibilities at once.
In Mathematics
When you see the plus-minus sign in mathematics, it usually means there are two possible answers to a problem. One answer uses the plus (+) part, and the other uses the minus (-) part.
For example, if you see "x = 5 ± 2", it means x can be two different numbers:
- x = 5 + 2, which is 7
- x = 5 - 2, which is 3
So, x could be 7 or 3. This is often used when solving equations, like those involving square roots.
In Science and Measurements
In science and measurements, the plus-minus sign is very important. It shows how accurate a measurement is. Scientists use it to tell you about the error or confidence interval in their findings.
Showing Measurement Error
When you measure something, like the length of a table, you might not get the exact same number every time. The plus-minus sign helps show how much your measurement might vary. For example, if a scientist measures a temperature as "25 ± 1 °C", it means the actual temperature is probably between 24 °C (25 - 1) and 26 °C (25 + 1). This range shows how certain they are about their measurement. It often represents the standard deviation or standard error, which are ways to describe how spread out the data is.
Showing a Range of Values
Sometimes, the sign can also mean an inclusive range of values. This means any value within that range is possible.
In Engineering
In engineering, the plus-minus sign is used to show tolerance. Tolerance is the acceptable range of values for something to work correctly or meet a standard.
For example, a machine part might need to be 10 millimeters long. But it's impossible to make it exactly 10.000000 mm every time. So, engineers might say "10 ± 0.1 mm". This means the part is acceptable if its length is between 9.9 mm and 10.1 mm. This ensures parts fit together and machines work safely.
In Other Fields
The plus-minus sign also appears in other areas:
In Botany
In botany, which is the study of plants, the sign is used in descriptions. It means "more or less." For example, a plant's leaf might be described as "5 ± 1 cm long," meaning it's around 5 cm, but could be a bit shorter or longer.
In Chemistry
In chemistry, the sign is used to show a racemic mixture. This is a special mix of two types of molecules that are mirror images of each other. They are present in equal amounts.
In Chess
In the game of chess, the plus-minus sign (±) can be used in notes to show that the white player has a clear advantage. The opposite sign, ∓ (minus-plus), means the black player has a clear advantage.
How to Say It
The plus-minus sign is usually pronounced "plus or minus" or simply "plus-minus."
See also
In Spanish: ± para niños
