Can you give us an example?
I don't believe the two ('in which' and 'whereby') function the same. It seems 'in which' is going to refer to a noun that does an action. Here is what Wiktionary.com had to say about "whereby":
Wiktionary Comment on 'whereby' wrote:
Use of whereby as a formal equivalent of where is nonstandard and is avoided by careful speakers and writers, who use where or in which instead. The term typically fails readability and comprehension review so it is generally avoided in published works. The term is also avoided by speakers as it makes it difficult to understand the message that's trying to be communicated.
If I see the term "whereby" in a SC question, I'm probably going to look for the sentence that doesn't use "whereby".
I've come up with a few examples of the proper usage of "in which":
1) The car, in which Jason rode, was a restored 1965 Mustang convertible.
2) Yesterday's game, in which she scored 3 goals, was her best game of the season.
These are not great examples. Each can be rewritten to be clearer such as:
1) Jason rode in a restored 1965 Mustang convertible.
2) She scored 3 goals in yesterday's game, her best game of the season. (I'm not sure I like this version better than my first attempt).
I hope this gives you some help. Generally, we want sentences and spoken English to be clear and understandable. When someone begins to use words and phrases such as "whereby" and "in which" I laugh to myself. Most of the time, the person is trying to sound intelligent. Few people actually have these words in the daily vocabulary.
Can you guys help explain when to use "in which" and "whereby" on gmat sentence correction...i'm stumped.
J Allen Morris
**I'm pretty sure I'm right, but then again, I'm just a guy with his head up his a$$.