Pre-Algebra

Probability tells how likely an event is, as a number from 0 to 1. Divide the number of favorable outcomes by the total number of outcomes. For a fair coin, the probability of heads is 1/2.

A box plot shows how a data set is spread out using five numbers: the minimum, the first quartile, the median, the third quartile and the maximum. The box covers the middle half of the data.

Dot plots and histograms show how often values appear in a data set. A dot plot puts one dot above a number line for each value. A histogram groups values into equal intervals and draws touching bars.

The mean is the average: add the values and divide by how many there are. The median is the middle value, the mode is the most common value, and the range is the largest minus the smallest.

A composite figure is a shape made of simpler shapes. To find its area, split it into rectangles, triangles or half circles, find each area, then add them or subtract any part that is cut out.

The area of a trapezoid is half the sum of its two parallel sides times its height: A = 1/2 × (b1 + b2) × h. For example, bases of 6 and 10 with a height of 4 give an area of 32.

The area of a rectangle is length times width, A = l × w. The area of a parallelogram is base times height, A = b × h. Area is the space inside a shape, measured in square units.

Perimeter is the distance all the way around the outside of a flat shape. Add the lengths of all the sides. For a rectangle, P = 2l + 2w. Perimeter uses length units like feet or meters.

The properties of numbers are rules that are always true for adding and multiplying: the commutative, associative, identity, inverse and zero properties. They tell you when you can change the order or grouping without changing the answer.

Rational and irrational numbers are the two kinds of real numbers. A rational number is any number you can write as a fraction of two integers, like or . Its decimal either ends or repeats. An irrational number cannot be written as a fraction. Its decimal goes on forever with no repeating pattern, like and…