"In which" is a modifier, and you could very well see it or other similar phrases on the GMAT (e.g. of which, for which, over which, etc.). Here are some examples of use:The Jerk
is my favorite movie in which Steve Martin starred.
During our school years, the area in which we lived was transformed.
In which century did King Henry II reign?
Notice that the statements could be phrased differently, avoiding "which," but doing so causes the awkward (but not tested by the GMAT) ending of a sentence with a preposition:
The Jerk is my favorite movie that Steve Martin starred in.
During our school years, there was a transformation to the area we lived in.
"Whereby" is a conjunction that means "by" or "through." It's akin to "by means of." Example:
We have a new computer system whereby
we can track all sales and shipments at all times.
But I can't recall seeing any instance of "whereby" on the GMAT. I think the GMAT would probably present the example above as:
We have a new computer system that allows us to track all sales and shipments at all times. (or)
We have a new computer system, making it possible to track all sales and shipments at all times.
Emily Sledge | Manhattan GMAT Instructor | St. Louis
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