2 (number)

2 (Two; ⁱ/ˈtuː/) is a number, numeral, and glyph. It is the natural number following 1 and preceding 3.

In mathematics

The number two has many properties in mathematics. An integer is called even if it is divisible by 2. For integers written in a numeral system based on an even number, such as decimal and hexadecimal, divisibility by 2 is easily tested by merely looking at the last digit. If it is even, then the whole number is even. In particular, when written in the decimal system, all multiples of 2 will end in 0, 2, 4, 6, or 8.

Two is the smallest and the first prime number, and the only even prime number (for this reason it is sometimes called "the oddest prime"). The next prime is three. Two and three are the only two consecutive prime numbers. 2 is the first Sophie Germain prime, the first factorial prime, the first Lucas prime, the first Ramanujan prime, and the first Smarandache-Wellin prime. It is an Eisenstein prime with no imaginary part and real part of the form 3n − 1. It is also a Stern prime, a Pell number, the first Fibonacci prime, and a Markov number—appearing in infinitely many solutions to the Markov Diophantine equation involving odd-indexed Pell numbers.

Number

A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, and so forth. A notational symbol that represents a number is called a numeral. In addition to their use in counting and measuring, numerals are often used for labels (as with telephone numbers), for ordering (as with serial numbers), and for codes (as with ISBNs). In common usage, the term number may refer to a symbol, a word, or a mathematical abstraction.

In mathematics, the notion of number has been extended over the centuries to include 0, negative numbers, rational numbers such as and , real numbers such as and , complex numbers, which extend the real numbers by including , and sometimes additional objects. Calculations with numbers are done with arithmetical operations, the most familiar being addition, subtraction, multiplication, division, and exponentiation. Their study or usage is called arithmetic. The same term may also refer to number theory, the study of the properties of the natural numbers.

Khan Academy

Khan Academy is a non-profit educational organization created in 2006 by educator Salman Khan with the aim of providing a free, world-class education for anyone, anywhere. The organization produces short lectures in the form of YouTube videos. In addition to micro lectures, the organization's website features practice exercises and tools for educators. All resources are available for free to anyone around the world. The main language of the website is English, but the content is also available in other languages.

History

The founder of the organization, Salman Khan, was born in New Orleans, Louisiana, United States to immigrant parents from Bangladesh and India. After earning three degrees from the Massachusetts Institute of Technology (a BS in mathematics, a BS in electrical engineering and computer science, and an MEng in electrical engineering and computer science), he pursued an MBA from Harvard Business School.

In late 2004, Khan began tutoring his cousin Nadia who needed help with math using Yahoo!'s Doodle notepad.When other relatives and friends sought similar help, he decided that it would be more practical to distribute the tutorials on YouTube. The videos' popularity and the testimonials of appreciative students prompted Khan to quit his job in finance as a hedge fund analyst at Connective Capital Management in 2009, and focus on the tutorials (then released under the moniker "Khan Academy") full-time.

Sesame Street

Sesame Street is a long-running American children's television series created by Joan Ganz Cooney and Lloyd Morrisett. The program is known for its educational content, and images communicated through the use of Jim Henson's Muppets, animation, short films, humor, and cultural references. The series premiered on November 10, 1969, to positive reviews, some controversy, and high viewership; it has aired on the U.S.'s national public television provider (PBS) since its debut, with its first run moving to premium channel HBO on January 16, 2016.

The show has undergone significant changes throughout its history. The format of Sesame Street consists of a combination of commercial television production elements and techniques which have evolved to reflect the changes in American culture and the audience's viewing habits. With the creation of Sesame Street, producers and writers of a children's television show used, for the first time, educational goals and a curriculum to shape its content. It was also the first time a show's educational effects were studied.

Fourth grade

Fourth Grade (also called Grade Four or Year five in Britain) is a term used to refer to a year of elementary education in some countries. In North America (with which region the term is usually associated thanks to its repetition in widely disseminated media sources) the fourth grade is the fourth school year after kindergarten. Students are usually 8-9 years old, depending on their birthday. It is a part of elementary school, a school providing instruction for young pupils, comprising the first three, four, or five grades of a student's educational career. Examples of lessons taught include - larger place value; how to write a good summary; writing with transitions; how to read large numbers; writing with starter sentence; and detailed sentences.

Argentina equivalent

In Argentina, the minimum age required for fourth grade is from 8 to 9 years old. In this instance, children who are in the middle of primary school performed the "confirmation of loyalty to the homeland," is an act in which children will have to swear to the Argentina country to "defend for the rest of his life". Sometimes children do a trip to Rosario, where raises the National Flag Memorial (Argentina).