NGSA Mathematics key terms

The value a digit has because of its position in a number. In 4,708 the 4 means four thousands, the 7 means seven hundreds, and the 8 means eight ones.

A way of writing a number as the sum of the values of each digit. For example, 3,562 is written as 3,000 + 500 + 60 + 2.

The usual way of writing a number using digits only, with each digit in its correct place. The standard form of three thousand fifty is 3,050.

Replacing a number with a nearby number of a chosen place value. Look at the digit to the right: 5 or more rounds up, 4 or less keeps the digit the same.

Finding an answer that is close enough for the purpose by using rounded or friendly numbers. It is used to check whether an exact answer is reasonable.

A whole number that divides another number with no remainder. The factors of 12 are 1, 2, 3, 4, 6, and 12.

The result of multiplying a whole number by another whole number. The first four multiples of 5 are 5, 10, 15, and 20.

A whole number greater than 1 with exactly two factors: 1 and itself. Examples are 2, 3, 5, 7, and 11.

A whole number greater than 1 that has more than two factors. For example, 9 has the factors 1, 3, and 9, so it is composite.

The largest number that divides two or more given numbers exactly. The greatest common factor of 18 and 24 is 6.

The smallest number that is a multiple of two or more given numbers. The least common multiple of 4 and 6 is 12.

Fractions that name the same amount even though their numerators and denominators differ. One half, two fourths, and three sixths are equivalent.

A fraction written so that the numerator and denominator share no common factor other than 1. Six eighths in simplest form is three fourths.

A number that is a multiple of the denominators of two or more fractions, allowing them to be added or compared. For one third and one fourth, 12 is a common denominator.

A number written with a decimal point to show whole units and parts of a whole. The digits to the right of the point stand for tenths, hundredths, and so on.

A ratio that compares a number to 100. Thirty percent means 30 out of every 100, which can also be written as 0.30 or three tenths.

A comparison of two quantities by division. A ratio of 3 to 5 can be written as 3:5 or as the fraction three fifths.

A ratio that compares quantities measured in different units. Traveling 120 miles in 2 hours gives a rate of 60 miles per hour.

A rate in which the second quantity is 1. If 4 notebooks cost 8 dollars, the unit rate is 2 dollars per notebook.

Any whole number, its opposite, or zero. Examples include -7, 0, 4, and 25; integers do not include fractions or decimals.

The distance a number is from zero on a number line, always zero or positive. The absolute value of -6 is 6.

A straight line on which numbers are placed in order at equal spacing, with zero marked and positive numbers to the right and negative numbers to the left.

The agreed sequence for evaluating expressions: grouping symbols first, then exponents, then multiplication and division left to right, then addition and subtraction left to right.

A small raised number that tells how many times a base is used as a factor. In 2 to the fifth power, 5 is the exponent and means five factors of 2.

A mathematical phrase made of numbers, variables, and operations but with no equals sign. For example, 4x + 7 is an expression.

A mathematical sentence stating that two expressions are equal, joined by an equals sign. For example, 3x + 2 = 14 is an equation.

A letter or symbol that stands for an unknown or changing number in an expression or equation. In 5n + 1, the letter n is the variable.

The number that multiplies a variable in a term. In the term 7y, the coefficient is 7; in -3x, it is -3.

Terms in an expression that have the same variable raised to the same power, so they can be combined. In 5x + 3 + 2x, the terms 5x and 2x are like terms.

An equation whose graph is a straight line and in which the variable is raised only to the first power. For example, y = 3x - 4 is linear.

A measure of how steep a line is, found by dividing the vertical change by the horizontal change between two points on the line.

A rule that pairs each input value with exactly one output value. A table or graph can show a function if no input has two different outputs.

A statement comparing two expressions that are not necessarily equal, using symbols such as <, >, or not equal to. For example, x > 5 means x is greater than 5.

The total distance around the outside of a closed figure, found by adding the lengths of all its sides. Perimeter is measured in linear units such as centimeters.

The number of square units needed to cover a flat surface. For a rectangle, area equals length times width.

The amount of space a solid figure occupies, measured in cubic units. For a rectangular prism, volume equals length times width times height.

The distance around a circle. It equals pi times the diameter, or about 3.14 times the diameter.

The distance across a circle through its center, equal to twice the radius. It is the longest chord of a circle.

The distance from the center of a circle to any point on the circle, equal to half the diameter.

A grid formed by a horizontal axis and a vertical axis that meet at the origin, used to locate points by ordered pairs of numbers.

Two numbers written in a fixed order, (x, y), that locate a point on a coordinate plane. The first number gives the horizontal position and the second gives the vertical position.

The average of a set of numbers, found by adding all the values and dividing by how many there are. The mean of 4, 6, and 8 is 6.

The middle value in a data set arranged in order. If there is an even number of values, it is the mean of the two middle values.

The value that appears most often in a data set. A set can have one mode, more than one mode, or no mode at all.

The difference between the greatest and least values in a data set. For the data 3, 7, 10, and 12, the range is 9.

A number from 0 to 1 that describes how likely an event is, often found by dividing favorable outcomes by all equally likely outcomes.

A single possible result of an experiment or event. Rolling a 4 on a number cube is one outcome of rolling the cube.

The set of all possible outcomes of an experiment. For one roll of a number cube, the sample space is 1, 2, 3, 4, 5, and 6.

An equation stating that two ratios are equal. For example, two thirds equals four sixths is a proportion.

A judgment about whether an answer makes sense in the context of the problem, often checked by estimation or by comparing with the given numbers.