Direct proportion can be thought of as ‘as one amount increases so does the other’, an example being the more potatoes you buy the more it costs.

e.g. two variables, x and y are in direct proportion to each other. Below is a table of results.

Note that proportion is preserved both vertically and horizontally on the table.

INVERSE PROPORTION

This can be thought of as “as one amount increases the other amount decreases”, an example being 2 men would take less time to dig a hole as one man would take to dig the same hole.

e.g. x varies indirectly with y Below is a table of results.

Find a formula connecting x and y and hence find he values of A and B

A and B would be worked out by substitution, as in the previous example.

Proportional parts (see ratio).