"A minute is not an hour."
Translation:Et minut er ikke en time.
I think it's better for you to just try to guess, maybe make the mistake, but then remember it better if you were wrong. I think one can develop an intuition for most words as to what gender they are and figure out the exceptions. I try to put the word in different contexts and figure out if it sounds wrong or not with en/et. At first you have no idea but after a while it gets better.
Tip : most words have the "en" gender. If you're to flip a coin, take "en" instead.
I agree with the others who have suggested that you present the correct indefinite as the first option. With new learners, it is important to keep the program consistent in its presentation of information. For all other examples I have encountered, the correct indefinite is always presented at the top of the list. Here? Not so, and that unintentionally reinforces misunderstandings. This needs to be fixed. "It's better to guess" is a lazy response for a mistake in the program.