The short version The mean is the average. Add every value, then divide by how many values there are. For 4, 8 and 6: 4 + 8 + 6 = 18, and 18 ÷ 3 = 6. Count every number in the list, including zeros and repeats. Missing one value in the count is the…
The short version A transversal is a line that crosses two or more other lines at different points. Crossing two lines creates eight angles, four at each intersection. When the two lines are parallel, corresponding angles, alternate interior angles and alternate exterior angles are all equal. Same side interior angles and same side exterior angles…
The short version A binomial is a polynomial with exactly two terms joined by a plus or minus sign, like x + 6, 3y – 5, or 4a² + 2b. To multiply two binomials, multiply every term in the first by every term in the second, then combine like terms: (x + 3)(x + 5)…
The short version Tau (τ) is a circle constant equal to a circle’s circumference divided by its radius. It works out to about 6.283185, which is exactly twice pi. So τ = 2π, and every formula you know still works. C = τr is the same statement as C = 2πr. Tau’s selling point is…
The short version A polygon is a flat, closed shape made of straight line segments that meet only at their endpoints. Three sides is the minimum. Circles, arcs, open shapes, and anything with a curve are not polygons, and neither are 3D solids like cubes. Polygons are named by side count: 3 triangle, 4 quadrilateral,…
The short version An equation is a math sentence saying two things are equal, with an equal sign in the middle: 3 + 2 = 5, or x + 4 = 10. An expression has no equal sign. 5x + 2 is an expression; 5x + 2 = 12 is an equation. You simplify expressions…
The short version A line plot stacks X marks (or dots) above a number line to show how many times each value shows up in a data set. To read one, find the value on the number line, then count the X marks stacked above it. That count is the frequency. To make one, draw…
The short version To simplify a fraction, find the greatest common factor (GCF) of the numerator and denominator, then divide both by it. 36/48 has a GCF of 12, and 36 ÷ 12 = 3 with 48 ÷ 12 = 4, so it becomes 3/4. If the GCF is hard to spot, divide by any…
The short version A hexagon is a closed, flat shape with six straight sides, six corners and six interior angles. The interior angles of any hexagon add up to 720 degrees. In a regular hexagon they’re all equal, so each one is 720 ÷ 6 = 120 degrees. Perimeter of a regular hexagon: 6 ×…
The short version A rhombus is a quadrilateral with four equal sides, opposite sides parallel and opposite angles equal. A slanted square, basically. Its diagonals cross at right angles, cut each other exactly in half, and each one splits the corner angles it passes through into two equal parts. Area works two ways: base ×…