Decimal division is when you know the product of two numbers and one of the factors, and you want to find the other factor. It’s the opposite of decimal multiplication. The main trick is to turn the divisor into a whole number and then do the division like you would with integers.

Decimal calculations are mainly taught from third to fifth grade. The depth of the content and the types of operations vary across different grades.

Decimal point, a math symbol, written as '.', used in decimal numbers to separate the integer part from the fractional part.

A divisor is a non-zero integer that can divide a number without leaving a remainder, also called a factor.

A divisor tree isn't a standard math concept; it's a problem-solving model used in algorithm competitions based on divisor relationships. It's often used to connect a number to the sum of its proper divisors, forming a tree structure to find the longest path.

Direct proportion is when two related quantities change together, and their ratio always stays the same.

Direct proportion and inverse proportion are mathematical concepts that describe how two related quantities change.

The diameter refers to a line that passes through the center of a circle and has both ends on the circle, usually represented by the letter d. It’s the longest line inside the circle and its length is exactly twice the radius.