This one's easy to explain, but unfortunately, it's also easy to miss!
I read your explanation, and I think that you are essentially right, but I just want to make sure.
(Now I'm going to copy some information from another post.)
Quote:
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5. The architecture exhibited in the Empire State Building and conveyed us an idea of the prevailing attitudes of the day is important for the historical and cultural value it represents.
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It's a bit tricky to answer these questions sometimes, but the main idea behind whether to choose the -ing form or the -ed form this:
When we reduce a verb to its -ing or -ed form, we must look at one and only one thing: whether the noun that it will modify is the
subject or
object of that verb.
The -ing form is used for DOING the action, which means SUBJECT, which means ACTIVE voice.
The -ed form is used for RECEIVING the action, which means OBJECT, which means PASSIVE voice.
Before I go further, let me offer two examples that will make things clearer as we go along:
- speaking person (the -ing form)
- spoken words (the -ed form)
In this type of question, we always have two elements:
- a particple, which is either in the -ing or -ed form
- a noun that is modified by this participle
So, using the previous examples,
speaking modifies
person and
spoken modifies
words.
The next step is to realize that these participles all come from verbs--
speaking and
spoken both come from the verb
speak.
Now, using these examples, and applying them to the rules I mentioned at the beginning, we will notice that if we made a sentence,
person would be the subject of the verb
speak and
words would be the object of the verb
speak. Using this procedure, we can figure out whether should use the -ing or -ed form of a participle that modifies a noun. And that's it!!
Of course, this is easy when the vocab is easy, and we often get confused when we are using difficult vocab because we sometimes don't know whether something is the subject or the object of the verb, but this procedure that I have explained is the only sure way to get the right answer.
In our sentence here,
which replaces
times, and
times is the
object of
determined, but it is the
subject of
differed.
In other words, we have something like this:
...somebody
determined times...
but
times differed...
I know some of you have learned that we should only use the -ing form only for actions that are ongoing/in progress in the present, but that's simply not true. We do
occasionally use them correctly for past actions that were ongoing/in progress.
Finally, everybody gets confused simply because the -ed form appears in the second one, making people think the -ed form should appear again when it's reduced. We need to realize that there is truly no connection (for our purposes here in GMATland, anyway
!!!!) between the two; it's
pure coincidence that each has the -ed form in it!!!
If you stick to the rules that I just wrote, you'll be okay.