Estonian Basic-School Mathematics Exam key terms

Counting number starting from 1 (1, 2, 3, …), used to count whole objects. Some textbooks include 0. In this exam natural numbers are the set for basic arithmetic and divisibility questions.

Whole number that can be positive, negative or zero, without a fractional part: …, −2, −1, 0, 1, 2, …. Used for temperatures, bank balances and positions on a number line.

Number that can be written as a fraction of two integers with a non-zero denominator, such as 3/4, −5 or 0.25. Its decimal form either ends or repeats periodically.

Real number that cannot be written as a fraction of two integers; its decimal expansion never ends and never repeats. Examples are √2 and π.

Number written as a quotient a/b, where a is the numerator and b the non-zero denominator. Shows a part of a whole and supports addition, multiplication and comparison of parts.

In a fraction a/b, the numerator a counts how many equal parts are taken and the denominator b tells into how many equal parts the whole is divided. Both must be handled in equivalent fractions.

Number written with a decimal comma, such as 3,75 or 0,125, where each place after the comma is a power of ten. Estonian notation uses a comma, not a point.

Rewriting fractions so they share the same denominator, usually the least common multiple, before adding or subtracting them. The value of each fraction stays unchanged.

Property of one whole number being divisible by another with no remainder. Divisibility rules for 2, 3, 5, 9 and 10 let you test this quickly from the digits.

Prime number that divides a given number exactly. Writing a number as a product of prime factors, such as 60 = 2·2·3·5, helps find common divisors and multiples.

Largest number that divides each of two or more given numbers without a remainder. Used to simplify fractions and to split quantities into equal groups.

Smallest positive number that is a multiple of each of two or more given numbers. Used to find a common denominator or when two events repeat together.

Amount left over after a division that does not come out exactly. For example, 17 divided by 5 gives quotient 3 and remainder 2.

Replacing a number by a nearby value with fewer significant digits, choosing the nearer option and rounding up when the first dropped digit is 5 or more. Used for estimates and sensible answers.

Rough scale of a number, usually its nearest power of ten. Checking the order of magnitude of a result quickly shows whether an answer is plausible.

Straight line on which every point corresponds to a number, with zero in the middle, positives to the right and negatives to the left. Used for comparing numbers and showing inequalities.

Distance of a number from zero on the number line, always non-negative. Written |−7| = 7 and |5| = 5; it ignores the sign.

In a power aⁿ, the base a is multiplied by itself n times and n is the exponent. Powers of ten make very large or small numbers compact.

Non-negative number whose square equals the given number: √49 = 7 because 7² = 49. Used in geometry, for example in the Pythagorean theorem.

Combination of numbers, variables and operation signs without an equals sign, such as 3x + 5 or 2(a − b). It can be simplified or evaluated for given values.

Removing brackets by multiplying each term inside by the factor outside, watching the signs. For example, 3(x − 2) = 3x − 6 and −(a + b) = −a − b.

Combining terms that have the same variable part into one term, for example 4x + 3x − x = 6x. Constants are combined separately to simplify the expression.

Statement that two expressions are equal, containing at least one unknown, such as 2x + 5 = 17. Solving means finding the values that make the statement true.

Value of the unknown that makes an equation or inequality true. It can be checked by substituting it back into the original statement.

Two or more equations that must hold at the same time, solved by substitution or elimination to find values satisfying all of them. Often used for two-unknown word problems.

Statement comparing two expressions with <, >, ≤ or ≥, such as 3x − 1 < 8. Its solution is a range of values, shown on a number line or as an interval.

General rule written with letters that expresses a relationship between quantities, such as A = πr² or s = vt. Used to calculate one quantity from known others.

Rule that assigns exactly one output value to each allowed input value. It can be given by a formula, a table or a graph.

Letter or symbol standing for a quantity that can change, such as x or t. In a function, the independent variable is the input and the dependent variable is the output.

Picture of a relationship drawn on coordinate axes, where each point shows an input and its output. Reading a graph means finding values, trends and key points from the drawing.

Two perpendicular number lines, the x-axis and y-axis, crossing at the origin. A point is located by an ordered pair (x; y) giving horizontal and vertical position.

Function with formula y = kx + b, whose graph is a straight line. The slope k shows how steeply the line rises or falls and b is the y-intercept.

Measure of how steep a line is: the change in y divided by the change in x between two points. Positive slope rises, negative slope falls, zero slope is horizontal.

Relationship where one quantity is a constant multiple of another, y = kx. Doubling the input doubles the output, and the graph is a line through the origin.

Relationship where one quantity increases as the other decreases so that their product stays constant, y = k/x. Its graph is a curve that never touches the axes.

Function of the form y = ax² + bx + c with a ≠ 0, whose graph is a parabola opening upward when a > 0. Its highest or lowest point is the vertex.

Perimeter is the total length around a plane figure; area is the size of its surface, measured in square units. Both are found from the figure's dimensions using standard formulas.

Amount of space a solid occupies, measured in cubic units. For a rectangular box it equals length times width times height.

Changing a measurement from one unit to another, for example 1 m = 100 cm or 1 m² = 10 000 cm². Area and volume units change by the square or cube of the length factor.

Property of figures with the same shape whose corresponding lengths are in a fixed ratio. Corresponding angles are equal, and areas scale by the square of that ratio.

In a right-angled triangle the square of the hypotenuse equals the sum of the squares of the other two sides: a² + b² = c². Used to find an unknown side length.

Ratios in a right-angled triangle: sine is opposite over hypotenuse, cosine is adjacent over hypotenuse, tangent is opposite over adjacent. They connect angles with side lengths.

Arithmetic mean: the sum of the values divided by how many there are. It describes a typical value but is affected strongly by very large or small data points.

Middle value of an ordered data set; with an even number of values it is the mean of the two middle ones. Half the data lie below it and half above.

Value that occurs most often in a data set. A set can have one mode, several modes, or none if all values appear equally often.

Number between 0 and 1 expressing how likely an event is, often found as favourable outcomes divided by all equally likely outcomes. It can also be estimated from relative frequency.

Count of how many times a value or event occurs in a data set, or that count divided by the total (relative frequency). Often shown in tables or bar charts.

Visual display of data such as a bar chart, pie chart or line graph. Choosing the right diagram and reading its scale correctly are key skills.

Problem set in a real-life situation, where you must identify the given data, choose the operations and answer the question asked. The final answer usually needs a unit and a sentence.

Approximate answer obtained by rounding the data to convenient numbers before calculating. It helps judge whether an exact result is reasonable.

Checking a result by substituting it back, using an estimate, or reversing the operation. It catches arithmetic slips and confirms the answer fits the situation.

Clear written reasoning that shows why a step or result is correct, referring to definitions, rules or calculations. Required in tasks that ask you to justify an answer.

Ordered written record of the steps taken to solve a problem, showing formulas, substitutions and intermediate results. Marks are often given for a correct method even if the final number is wrong.