Here is an app that should come useful for people poor in numbers. Math Ref is a math reference app. It includes formulas, tips, and examples from many areas of mathematics. Math Ref has the potential to be a very helpful tool once some errors are fixed and the organization becomes more intuitive.

Upon launching Math Ref, you are given a list of topics. Tapping on a topic will give a list of sub-topics. Choosing one of these sub-topics will provide a page of definitions, formulas, figures, and equations relevant to the chosen topic. Tapping a definition, formula, figure, or equation will usually give more information about it. Many times this information is some historical background about the topic.

(Source) The iPhone Blog