Education? Examination ?
And 6th ratios? Eh? What are they??…
Rather than a tool for calculation, this presents* as a test of knowledge, as if examining previous tuition the user is assumed to have received. More obvious is that the developer has made considerable effort; but the app overlooks a fundamental of education in not reviewing the required method, thus muddying its own purpose.
*Perhaps there is a demonstration or clarifying example buried within but if so, I didn't see it.