This playground is running off a mix of language implementations and frameworks and has been setup to demo/prove some concepts with regards the language and or framework.
 
At the same time though, i thought it would be useful to start putting together an area where an application of compound interest provide some value- all geared towards a practical learning in mathematics.
 
Using CodeIgniter, a PHP MVC framework, we have a calculator for compound interest, amortization and doubling (halving) time for the value of money.
 
Then, using Javascript, we have a statistics calculator. A basic calculator for quickly finding the size, median, mean, variance and standard deviation of a given dataset.
 
Extending on that concept, there's also now a two-variable statistics calculator which can be used to determine the (linear) relationship between two variables. A graph is also included to visually display the scattered points and a calculated least squares line.
 
And then we have Morty, a Ruby on Rails implementation for an amortization schedule. Note; this is hosted on Heroku. It's close relative, Mortpy is living across the highway, at AppEngine and is Python-flavoured.
 
And then... there's the South-African based PAYE interactive calculator which simply, and quickly calculates your tax contribution based on either monthly or annual taxable income. This is part of my zaFin project, which also includes yet another simple amortization calculator nicknamed MortyJs.
 
Source Code: All the source code for these utilities are provided under various Open Source licences. If you can't find the link to download it, and you want to use it, let me know, i will make an effort to send you a copy via email.
 
If you find any of these online utilities or free code useful, the best way to say thanks is to buy me a coffee ;)

Thank you