Here in Cambodia there's a fairly unique two-currency system in use, and it often gets really confusing to work out if you're getting the correct change.
The local currency is the Cambodian riel and the de facto currency is the US dollar.
There are no US coins here. In common street transactions USD $1 is equal to KHR 4,000. (Though at a money changer it's more like 4,100 riel to the dollar, it's not relevant for this question.)
So very often riel notes are used as the equivalent to coins and you have to do some tricky mental arithmetic to calculate what your change should be.
- You might be given a price in dollars and cents, in dollars and riels, or just in riels.
- You might receive your change in dollars and riels, or just in riels.
So I'm looking for an app or website that can do these calculations for me, more reliably than my poor little brain.