General Aptitude · topic
Counting with and without order, restrictions, circular and identical arrangements, distributions and derangements; arithmetic, geometric and pattern series; mean, median, mode, range and standard deviation; classical probability, complements, independence, at-least-one and binomial counts.
Elementary statistics summarises a list of numbers by a centre (mean, median, mode) and a spread (range, variance, standard deviation). Elementary probability measures how likely an event is, usually as a ratio of counts or as a product of the probabilities of successive steps.
To count arrangements or selections without listing them, use two principles (add for "or", multiply for "and then") and two questions about the objects: does order matter, and is repetition allowed.
A sequence of terms is given, and the task is to find the next term, a missing term, the term that breaks the pattern, or the sum of many terms. Two methods apply. The first is algebraic: the arithmetic and geometric progressions and the standard sums, where the answer follows from a formula.
One-page visual sheets for this topic, in the sheet library on the store. Previews are free; the full sheets come with the subject pack.
