Learn Swedish: Hon har varit vaken i sextio timmar. - She has been awake for sixty hours.

In Swedish, we use i to talk about how long an ongoing activity or state lasts (like being awake). You use på when talking about how long it takes to finish an action, or when saying you haven't done something for a certain amount of time. Since she was continuously awake for this entire duration, i is the correct choice.

Does the word vaken change depending on who is awake?

Yes! Vaken (awake) acts as an adjective here, so it has to match the subject. Because hon (she) is an en-word, we use the basic form vaken. If it were a plural subject like de (they), you would use the plural form vakna (De har varit vakna...).

Is sextio pronounced exactly how it's spelled?

Not quite! While it is spelled sextio, it is usually pronounced "sexti" in everyday speech. This dropping of the final "o" sound happens with most multiples of ten in Swedish, such as femtio ("femti") and sjuttio ("sjutti").

What is the singular form of timmar?