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in which vs when

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by prachi18oct » Fri Jun 27, 2014 1:32 am
OG 12 #70

His studies of ice-polished rocks in his Alpine
homeland, far outside the range of present-day
glaciers, led Louis Agassiz in 1837 to propose the
concept of an age in which great ice sheets had
existed in now currently temperate areas.
(A) in which great ice sheets had existed in now
currently temperate areas
(B) in which great ice sheets existed in what are
now temperate areas
(C) when great ice sheets existed where there were
areas now temperate
(D) when great ice sheets had existed in current
temperate areas
(E) when great ice sheets existed in areas now that
are temperate

The explanation says that the usage of "in which" and "when" both are correct here.
But I do not understand how?
when great ice sheets existed in what are now temperate areas...is this also correct?
"in which/when great ice sheets existed" both of them modify noun "age"
how to decide if the usage of "in which" is correct???

Please explain.
Last edited by prachi18oct on Fri Jul 17, 2015 9:28 am, edited 1 time in total.
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by sukkhi » Sun Jun 29, 2014 12:13 am
prachi18oct wrote:OG 12 #70

His studies of ice-polished rocks in his Alpine
homeland, far outside the range of present-day
glaciers, led Louis Agassiz in 1837 to propose the
concept of an age in which great ice sheets had
existed in now currently temperate areas.
(A) in which great ice sheets had existed in now
currently temperate areas
(B) in which great ice sheets existed in what are
now temperate areas
(C) when great ice sheets existed where there were
areas now temperate
(D) when great ice sheets had existed in current
temperate areas
(E) when great ice sheets existed in areas now that
are temperate

The explanation says that the usage of "in which" and "when" both are correct here.
But I do not understand how?
when great ice sheets existed in what are now temperate areas...is this also correct?
"in which/when great ice sheets existed" both of them modify noun "age"
how to decide if the usage of "in which" is correct???

Please explain.

if the "time" given is period,age,etc. and not a specific point on timeline --it's ok to use "in which" whereas "when" can be used in both instances.

e.g. usain bolt raised his country flag when he reached the finish line.

here "in which" cant be used because we're talking about specific time not a range of time in which it could have happened.
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by GMATGuruNY » Sun Jun 29, 2014 3:11 am
prachi18oct wrote:OG 12 #70

His studies of ice-polished rocks in his Alpine
homeland, far outside the range of present-day
glaciers, led Louis Agassiz in 1837 to propose the
concept of an age in which great ice sheets had
existed in now currently temperate areas.
(A) in which great ice sheets had existed in now
currently temperate areas
(B) in which great ice sheets existed in what are
now temperate areas
(C) when great ice sheets existed where there were
areas now temperate
(D) when great ice sheets had existed in current
temperate areas
(E) when great ice sheets existed in areas now that
are temperate

The explanation says that the usage of "in which" and "when" both are correct here.
But I do not understand how?
when great ice sheets existed in what are now temperate areas...is this also correct?
"in which/when great ice sheets existed" both of them modify noun "age"
how to decide if the usage of "in which" is correct???

Please explain.
A when-clause can serve to modify a noun that refers to TIME:
an age WHEN great ice sheets existed

Generally, preposition + which serves to modify the nearest preceding noun.
In these cases, which will serve to stand in for the modified noun.
an age in which great ice sheets existed
To determine whether in which is viable here, replace which with the modified noun -- an age -- to confirm that the resulting meaning makes sense:
great ice sheets existed IN AN AGE
Since it makes sense to say great ice sheets existed IN AN AGE, there is no error.

An important take-away:
NOT ALL SPLITS ARE MEANINGFUL.
Here, the split between when and in which has no bearing on the correct answer, since both when and in which can serve to modify an age.
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