Addition : Addition is the mathematical operation that describes increasing a number by an amount equal to a second number. The mathematical symbol for addition is the plus sign $+.$ The term addition is also used for a generalization of this basic operation on numbers to functions, vectors and matrices.

Hundred : Hundred refers to the number 100.

Ones digit : The first digit left of the decimal point (or the digit furthest to the right if there is no decimal point). It counts multiples of 1.

Subtraction : Subtraction is the mathematical operation that describes decreasing a number by an amount equal to a second number. The mathematical symbol for subtraction is the minus sign $-.$ The term subtraction is also used for a generalization of this basic operation on numbers to functions, vectors and matrices.

Tens digit : The tens digit is the second digit left of the decimal point. For example 31.2 and 32 both have tens digits equal to 3.

Hundred : Hundred refers to the number 100.

Increasing : Increasing means getting bigger.

Nearest ten : Rounding to the nearest ten refers to rounding such that the resulting number is a multiple of ten. If the ones digit is 5 or more the tens digit is rounded up, otherwise it is rounded down.

Number : A number $x$ is a mathematical symbol representing a quantity.

Ones digit : The first digit left of the decimal point (or the digit furthest to the right if there is no decimal point). It counts multiples of 1.

Round : Round can be a property of a shape, meaning that it does not have any corners. For example a circle can be described as round. A number can be informally described as round if it does end in one or several zeros such that rounding that number to a certain number of digits does not change the number.

Rounding : Rounding is the operation of changing a number to a number that is close to the original number. Rounded numbers are often used to do quick rough calculations for estimation purposes. For example rounding $4549$ to the nearest thousand results in 5000, rounding the same number to the nearest hundred results in 4500. In general one rounds up if the digit after the digit we try to round to is 5 or more, otherwise one rounds down.

Tens digit : The tens digit is the second digit left of the decimal point. For example 31.2 and 32 both have tens digits equal to 3.

Box plot : A way to visualize data. The left end of the box plot coincides with the minimum of the data. Similar the right end of the box plot visualizes the maximum of the data. The left and right end of the box in the box plot correspond to the 25th and 75th quantile of the data and the line in the box represents the median of the data.

Line : A line AB is a one-dimensional shape that includes the points A and B, all the points on the line segment in between A and B and all the points of the straight extension of the line segment beyond A and B. A line does not have an endpoint.

Median : The median of n numbers is defined as the $\frac{n}{2}$-th biggest number in case of even $n$ and as the average of the $\frac{n-1}{2}$-th biggest number and the $\frac{n+1}{2}$-th biggest number in case of odd $n.$ The median of numbers is a statistic that can be representative of a typical element of a collection of numbers. It is an alternative to the average of numbers.