How should you know if you should use the compound interest formula or the continuous interest formula?

Do you mean

$$FV=PV*e^{kt}$$

Could you please give us a question to show you on?

Well that's the question I was struggling with but then my teacher told me that in the question it would be given that the sum has to be compounded annually or half yearly or by using simple interest ! It would all be given like how much will $45 be after two years at the rate of 5% compounded annually? So like that it would be given and you just have to use the formula with a sprinkle of your brain!