What is an inverse variation?
Inverse Variation occurs when one variable increases while another decreases. For instance, the more painters that are painting a house lowers the amount of time that would be spent painting. The following videos explain inverse variations in the HSC Standard Math course.
This video goes through a worked example from the mathematics course, and is something similar to what you will be asked in your HSC.
If you need more help understanding inverse variations, this video is extremely useful in helping you understand the algebraic aspect of the formula.