Given the examples, how is anyone to know this? I guess and got it right, but speed is not one of the words.
You're right, there was no hint, it's added now.
'cepat' (adjective) = fast.
'cepat' + 'ke-an' affix = kecepatan (noun) = speed, velocity.
Should it not be waktu instead of ketika?
I still found this sentence awkwardly phrased
Maybe its better to use dia instead of nya because its hard to know how to use nya without context, especially when the whole phrase is just awkward
I thought it was "the" like its been for previous exercises.