An enlargement is a scaled up (or down) version of a figure so that the new figure is in proportion to the original figure. The relative positions of points are unchanged and the two figures are similar.

In the diagram below triangle A'B'C' is the image of triangle ABC under the enlargement with enlargement factor 2 and centre of enlargement O.

Equally likely outcomes have the same probability of occurring. For example, in tossing a fair coin, the outcome ‘head’ and the outcome ‘tail’ are equally likely. In this situation,

\(Pr(\text{head})\;=\;Pr(\text{tail})\;=\;0.5\).

An equation is a statement that asserts that two mathematical expressions are equal in value. An equation must include an equal sign.

Examples of equations are \(3+14=6+11\) or \(2x+ 5=21\).

Equivalent fractions are alternative ways of writing the same fraction; for example, \(\frac12=\frac24=\frac36\cdots\). Two fractions \(\frac ab\) and \(\frac cd\) are equivalent, if they are equal in value, that is, if \(ad=bc\).

To estimate is to judge the value, number, or quantity of a calculation roughly.

In statistical terms, an estimate is information about a population extrapolated from a sample of the population; for example, the mean number of decayed teeth in a randomly selected group of eight-year-old children is an estimate of the mean number of decayed teeth in eight-year-old children in Australia.

An *even number* is an *integer* that is *divisible* by 2. The even numbers are

An *event* is a *subset* of the *sample space* for a *random experiment*; for example, the set of outcomes from tossing two coins is {HH, HT, TH, TT}, where H represents a ‘head’ and T a ‘tail’.

An exponential function is a function where the independent variable is in the exponent (or index), that is, in the simplest form, \(\;f(x)=a^x\), where a is a positive real number not equal to zero.

An expression refers to two or more numbers or variables connected by operations. For example, \(17–9, 8×(2+3), (2a+3b)^2\) are all expressions. Expressions do not include an equal sign.