Some calculations are done according to some legal rule. For example, if you want to calculate how much income tax has to be paid on a taxable annual income of €79.245,18 in Germany, there is only one correct answer. You get it right or you get it wrong. If you get it right, you don't need to explain how floating point arithmetic works. If you get it wrong, you don't need to explain how floating point arithmetic works, you have to fix your broken code.
Sometimes you display results that don't look right. For example, if you convert US$ 13,297.46 into UK£ with two decimal digits, and then convert that amount of UK£ back to US$, you might not get US$ 13,297.46 but US$ 13,297.45 or US$ 13,297.47. That has nothing to do with floating-point arithmetic. It's an unavoidable problem and you better be able to explain why it is unavoidable. (You should also know why the problem doesn't happen when you convert from UK£ to US$ and back).
There are other possible results that don't look right. If you convert numbers to percentages the percentages should add up to 100%, but they might not. If you display four percentages with two decimals, the four displayed percentages might add up to 99.99% or 100.01%. Nothing to do with floating-point arithmetic. Still you should be able to explain why.
Next, there are situations where careless use of floating-point arithmetic leads to inappropriate results. For example, a + b + c is usually not the same as b + c + a. If that causes a problem, there is nothing to explain, it's something that you fix.