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# Double|Definition & Meaning

## Definition

The term **“double”** can mean two things: to **make** **twice** (multiply by 2) or to have **two of something**. The first usage is much more common. If you had **2 apples** and you plucked **2 more**, you **doubled** the number of apples you had. However, “working double shifts” means that a person works on both the morning and evening shifts and this is **not a multiplication by 2.**

The concept of **doubling** can also be applied to other **areas of mathematics**, such as **geometry** and **algebra.** **In geometry**, for example, a line segment can be said to be **double** the length of another line segment if its length is **twice as long.**

**In algebra**, the concept of **doubling** can be used to solve equations by **isolating** a variable on **one side** of the equation and then **multiplying or dividing it by 2**.

## Different Ways to Double

The concept of **doubling** is a fundamental concept in mathematics that is used in a variety of **different contexts**. And there are multiple ways for it.

### Addition

You can use the “**+**” operator to **double** a number, for example:

number + number = double

For example: 5 + 5 = 10

Another way to **double** a number is** to add it to itself**. For example, if you want to double the number** 5**, you would perform the calculation **5 + 5 = 10**. The result, **10**, is the **double** of the original number** 5.**

### Multiplication

In multiplication, you simply need to** multiply it by 2**. For example, if you want to double the number** 5,** you would perform the calculation **5 * 2 = 10**. The result,** 10**, is the **double** of the original number** 5.**

### Subtraction

In subtraction, the concept of **“doubles”** is often used as a strategy to make the problem **easier to solve**. The strategy of using doubles in subtraction involves **breaking down** a subtraction problem into** two parts**, each of which is half of the original problem.

For example, let’s say you want to subtract the number **15** from the number** 20.** Instead of subtracting 15 from 20 directly, you can use the strategy of** doubles by** breaking the problem down into two parts:

**Subtracting 10 from 20****Subtracting 5 from 10**

The first step is to subtract **10 from 20**, which gives you the result of **10**. The second step is to subtract **5 from 10**, which gives you the final result of** 5.**

By breaking down the subtraction problem into two parts, each of which is half of the original problem, you can use the concept of doubles to make the problem **easier to solve.** This strategy can also be applied to subtraction problems involving larger numbers. For example, if you wanted to subtract** 38 from 50,** you could break the problem down into two parts:

**Subtracting 25 from 50****Subtracting 13 from 25**

The first step is to subtract **25 from 50**, which gives you the result of **25**. The second step is to subtract **13 from 25,** which gives you the final result of **12.**

This method is particularly useful for **young students** and people who are learning subtraction. It can help them to understand the subtraction concept and make it more **manageable.**

**Double in Computer Science**

In computer science, the term **“double”** is used to describe a data type that can store a number with **twice** the precision of a single-precision** data type.** This data type is often used to represent **decimal numbers** and is commonly used in scientific and engineering calculations.

A **double-precision** floating-point number is a type of number that uses **64** bits of memory to store its value. This allows for a much** larger range of numbers** to be represented compared to a **single-precision** floating-point number, which only uses **32** bits. The double-precision also provides** greater precision**, meaning that it can represent decimal numbers with more digits after the decimal point.

For example, a **single-precision** floating-point number can represent the value 3.14159265 up to** 7 decimal places**, while a **double-precision** floating-point number can represent the value up to **15 decimal places** 3.141592653589793.

Because of the** increased precision and larger range of numbers** that can be represented, double-precision floating-point numbers are often used in** scientific and engineering calculations** where a high level of precision is required. For example, in simulations, weather forecasting, and other high-precision numerical computations.

It’s important to note that while double-precision floating-point numbers provide greater precision than single-precision floating-point numbers, they are still not capable of **representing certain numbers** exactly, such as some irrational numbers. Therefore, it’s important to be aware of the** limitations** of this data type when using it in computations.

Overall, the double data type is an **essential** tool in computer science, and it’s used in many applications that require high precision and large range of **numbers representation**. It is a fundamental concept that is used in a variety of different areas, such as scientific and engineering calculations, simulations, and other high-precision numerical computations.

It’s also possible to use a** programming language to double a number** by using the appropriate operator or function. For example, in **Python**, you could use the** “*”** operator to **double** a number:

x = 5 # integer 5

x = x * 2 # multiplies by 2 (double)

print(x) # Output: 10

The above code takes the number 5, multiplies it by 2 (doubles it), and then prints (shows to the user) the output, which would be 10.

In **C++**, you could use the** “*”** operator as well:

int x = 5; // integer 5

x = x * 2; // multiply by 2 (double)

cout << x; // Output: 10

The above code does the same thing as the previous one, just in a different programming language.

In most programming languages, there is usually a function or **operator** that can be used to **double** a number; it’s just a matter of finding the correct one for your specific language or context.

## Example Question

Q: If the length of a rectangle is double the width, and the perimeter is 40, what is the length of the rectangle?

### Solution

Let’s call the width of the rectangle “w” and the length of the rectangle “l.”

From the problem statement, we know that the length of the rectangle is double the width, so we can write the equation: l = 2w

We also know that the perimeter is 40, and the perimeter of a rectangle is given by the formula: P = 2l + 2w

Substituting the first equation into the second equation, we get: 40 = 2(2w) + 2w 40 = 6w

Now we can solve for the width by dividing both sides by 6: w = 40/6 w = 6.67

Finally, we can use the equation l = 2w to find the length of the rectangle: l = 2(6.67) l = 13.33

Therefore, the length of the rectangle is 13.33 units.

*All mathematical drawings and images were created with GeoGebra.*