Hi

I am not sure on when to use double, twice, increase or two times

Regards,
Roger

well, i'll start by pointing out the obvious: unlike the other 3 constructions you've mentioned, 'increase' can refer to an increase of any size. so, if you don't actually mean 'double', then you need to use a more general term, like 'increase'.

the gmat would almost certainly prefer 'twice' to 'two times', because 'twice' is nice - it's more concise.

'double' is most often found as a verb.

have you seen any problems that focus on this distinction?

Thanks Ron

I will post a sentence as soon as I come across one.