Ratio, proportion and rates of change. NEW: Equivalent ratios and simplifying ratios. Revise how to work out equivalent ratios and simplify ratios by dividing both sides by the highest common factor.

This article was originally published with the title “ A Brief History of Aspect Ratios, aka Screen Proportions ” in Scientific American Magazine Vol. 318 No. 3 (March 2018) doi:10.1038 ...

A proportional spread is the ratio of a security's bid and ask price distance relative to the security's price. It is wider in less liquid securities and tighter in more liquid ones, ...