Integers can be divided into positive integers, zero and negative integers. When a number belongs to one of these categories, it is called an integer. Fraction refers to the ratio of a positive integer a to a positive integer b that is not equal to an integer. Numbers that are not integers are fractions. For example, one half, three eighths and one quarter.

If the last digit of a number is an even number, the number is divisible by 2. If the sum of a number is divisible by 3, then this integer can be divisible by 3. If the last two digits of a number are divisible by 4, then the number is divisible by 4. If the last digit of a number is 0 or 5, the number can be divisible by 5. If a number is divisible by 2 and 3, it is divisible by 6.

Fractions are formed by putting molecules on the denominator, and there are no stripes between molecules. In Sanskrit literature, fractions are always expressed as addition and subtraction of integers. Integer is written in one line, and its score is written in the next line of two lines. If the score is in a small circle, subtract it from the integer. If such a sign does not appear, it is understood as adding.

Extended data

The family of numbers is further expanded, including real numbers and imaginary numbers, and addition, subtraction, multiplication and division are extended to include power sum roots, forming a new branch of mathematics "algebra". Algebra has made further progress in two aspects. One is to study linear equations with many unknowns, and introduce symbols and concepts such as matrix, vector and space to form "linear algebra".

If one digit of a number is truncated, 5 times of the one digit is subtracted from the remaining number. If the difference is a multiple of 17, the original number can be divisible by 17. If the difference is too big or it is not easy to see whether it is a multiple of 17 in mental arithmetic, repeat the previous process until it can be clearly judged.

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