She thinks going to the gym a waste of time

[ROBINDESBOIS]

She thinks going to the gym a waste of time.
Is that sentence correct despite the fact that Is is missing?

[poli]

She thinks going to the gym a waste of time.
Is that sentence correct despite the fact that Is is missing?
It is incorrect, but you can say, she thinks going to the gym is a waste of time,
Oddly you can say (especially in Britain), she thinks it a waste of time.

[ROBINDESBOIS]

I found it in a Proficiency book and they stated as correct . It sounded weird to me !

[poli]

To me too, but perhaps it is used in Great Britain. I know, she thinks it a waste of time, is used especially on your side of the Atlantic. Where was the proficiency book published?

[ROBINDESBOIS]

In Great Britain, Exeter.

[poli]

That explains it. There are slight differences in the use of language in European and American English.