# Fuzzy number

A fuzzy number is a real number with an associated membership function that expresses the degree to which the number is considered to be a member of a given set. In other words, a fuzzy number is a number with a "fuzzy" boundary, rather than a sharp boundary.

Fuzzy numbers are often used in situations where it is difficult to assign a precise value to a quantity, such as in the case of human opinions or judgments. For example, if you ask a group of people to rate their level of satisfaction with a product on a scale of 1 to 10, you will likely get a range of answers, with some people saying they are very satisfied (9 or 10), some people saying they are somewhat satisfied (7 or 8), and some people saying they are not very satisfied (5 or 6). These different responses can be represented by a fuzzy number.

Fuzzy numbers can also be used in mathematical models to represent imprecise or uncertain data. For example, in a model of population growth, the population size at any given time may be represented by a fuzzy number, since it is difficult to predict exactly how many people will be born or die in a given year.

Fuzzy numbers have many applications in engineering and economics, as well as in other fields where precise values are difficult to determine.

#### What are the types of fuzzy numbers?

There are four types of fuzzy numbers:

1. Left-shoulder fuzzy numbers: these have a left-shoulder shape, with a sharp peak at the left side and a gradual tail off to the right. An example would be a grade of "C" in a class, where a "C" is defined as a score between 70-79%.

2. Right-shoulder fuzzy numbers: these have a right-shoulder shape, with a sharp peak at the right side and a gradual tail off to the left. An example would be a grade of "B" in a class, where a "B" is defined as a score between 80-89%.

3. Symmetric fuzzy numbers: these have a symmetric shape, with a sharp peak in the middle and a gradual tail off to the left and right. An example would be a grade of "A" in a class, where an "A" is defined as a score between 90-100%.

4. Bell-shaped fuzzy numbers: these have a bell-shaped curve, with a gradual tail off to the left and right. An example would be a grade of "D" in a class, where a "D" is defined as a score between 60-69%.

### How do you find a fuzzy number?

There is no definitive answer to this question as there is no single method that is guaranteed to work for all fuzzy numbers. However, there are a few approaches that may be useful in some cases.

One approach is to use a graph or plot to visualize the fuzzy number. This can be helpful in understanding the shape of the fuzzy number and identifying any potential patterns.

Another approach is to use a numerical method, such as the bisection method, to approximate the value of the fuzzy number. This can be useful if the exact value is not known but it is possible to bound the number.

Finally, it is also possible to use a heuristic approach to finding a fuzzy number. This means using intuition and experience to try to find a good estimate for the value of the number. This approach is often used when no other information is available.

### Why do we use fuzzy numbers?

Fuzzy numbers are used in mathematical modeling to deal with imprecise or uncertain data. They are often used in decision-making situations where the information is incomplete or ambiguous.

Fuzzy numbers can be used to represent both qualitative and quantitative information. For example, a qualitative statement such as "this is a large number" can be represented by a fuzzy number. Similarly, a quantitative statement such as "this number is between 10 and 20" can also be represented by a fuzzy number.

Fuzzy numbers have many advantages over traditional (non-fuzzy) numbers. They allow us to more accurately represent imprecise or uncertain information. They also can help us to make better decisions in situations where the information is incomplete or ambiguous.

### What is fuzzy set with example?

A fuzzy set is a set where the membership of each element is not either completely true or completely false, but instead is a value somewhere between 0 and 1.

For example, let's say we have a set of people. We could say that each person in the set is either a member or not a member. In this case, each person would have a membership value of either 1 (for being a member) or 0 (for not being a member).

However, in a fuzzy set, the membership values would be somewhere between 0 and 1. So, for example, we could have a person with a membership value of 0.5, meaning that they are only partially a member of the set.