Hint: Design a calculator. Standard, scientific, or specialty calculator for something such as a mortgage? Is it for a phone, a tablet, a web app?
I decided to create a mobile foreign exchange calculator inspired by a combo of the following web-based FX calculators:
Instead of tapping a “convert” button, I think it’s more worthwhile to have a real-time calculation much like how Google’s FX calculator works: https://www.google.ca/search?q=google+foreign+exchange+calculator