Introduction to fractions

Defining Fractions

Equal shares of a whole.

A fraction shows a part of a whole object. Imagine a pizza cut into slices; a fraction tells you how many slices you have compared to the whole pizza. We write it as

\frac{a}{b}

Key Points

The bottom number is the denominator. It tells you the total number of equal slices the pizza was cut into.
The top number is the numerator. It tells you how many of those slices you actually have.
The parts must be exactly the same size. If the slices are unequal, you cannot write them as a simple fraction!

Olympiad Fact

Remember: Numerator is North (top), Denominator is Down (bottom). The fraction bar also acts as a division sign: $a/b$ is the same as $a \div b$ .