Helper verbs in comparison SC Questions

[ParthJ26]

Dear Sage, Hi. Hope you're well!

SC Guide 6th Edition. Pg 202. Top.

# 1. I HAVE never SEEN an aardvark, but last year my father DID. - WRONG. (because the first instance of the verb should match the helping verb in tense)

# 2. Since 1990 the global economy HAS GROWN more than it DID during the 10,000 years from the beginning of agriculture to 1950 - CORRECT OG OA.

Here, the first instance of the verb does not match the helping verb in tense. I have quoted some points from that post.

RON:

that's not accurate. in fact, one of the prime uses of helping verbs in parallel constructions is to express the same verb in a different tense.

we may already have gotten rid of that "rule" in the 5th edition books.

https://www.manhattanprep.com/gmat/foru ... k&start=30

RON:

in general,

1 * if you have than/as + subject + FORM OF "TO BE" as the second half of a comparison, then you must have another form of "to be" in the first half of the comparison.
or, there should be something in the first half that would make sense with "to be" in front of it.

2 * if you have than/as + subject + HELPING VERB as the second half of a comparison, you can have just about any other form of the same verb in the first part, as determined by context.

3 * if you have than/as + subject + FORM OF "TO DO" as the second half of a comparison, then you must have an ACTION VERB[/b] (or another form of "to do") in the first half of the comparison.

here are some examples:
#1
see the post directly above this one.
also
parking spots are disappearing much more quickly today than they were yesterday.
#2
james can negotiate with salespeople more effectively than stephanie can. (comparing their abilities)
james can negotiate with salespeople more effectively than he does. (his ability exceeds his actual performance, probably because he just isn't trying very hard)
#3
parking spots disappeared much faster today than they did yesterday.
tanya eats more slowly than she did when she was a teenager. (note that "did" doesn't have to have the same tense as the action verb)

But my question still stands:

Which one of the 2 sentences that I mentioned at the beginning of the post is correct? Are both correct? If yes, then why?

What is the gap in my learning that I need to fill?

Thanks a lot, Sage. You've truly been phenomenal!

Parth Jain

[Sage Pearce-Higgins]

You're right to flag up that example from page 202 of the SC guide. I'm inclined to agree with Ron that the example about the aardvark is actually okay, especially in the light of the OG example you've found. I'll confer with my colleagues on that one. Remember that Official correct answers are always correct, there's no point questioning them. Actually, when we write our example problems, official correct answers are the best guide we have to the style and rules that GMAT follows.

Notice that the other examples we give on page 202 involve some problem with the meaning of the sentence. That's the ultimate point of good parallelism (and other grammar) - is the meaning clear?

However, we may be splitting hairs here. GMAT problems are multiple choice, so we can compare answers and work by elimination. You can trust that there's always something significantly wrong (not just 'borderline') with wrong answer choices.

[JbhB682]

Hi Sage

Ron mentioned the following post below

3 * if you have than/as + subject + FORM OF "TO DO" as the second half of a comparison, then you must have an ACTION VERB[/b] (or another form of "to do") in the first half of the comparison.

Per my understanding, forms of to-do are only of three types : does / did / do

But how does this bode with this example (made up)

I can eat as much food as my grandfather did

In this case, in the second half --- "Did" is a form of "To do" ....

However in the first half -- i neither have an action verb nor a form of "to do" .... "Can" is a helping verb

Doesn't this go against bullet point 3 ?

[Sage Pearce-Higgins]

I can eat as much food as my grandfather did

I would be very suspicious about this sentence. You're right - it breaks the rule that Ron laid out and it seems to make an comparison that isn't parallel. However, the meaning seems clear enough. In conclusion, I wouldn't expect either to see a construction like this one in a correct GMAT SC problem (but please prove me wrong and show me one!) or to find it as a deciding difference between two answer choices.

[JbhB682]

Hi Sage --

For these sentences -- for construction two, which helping verbs is Ron talking about

Are these verbs that are NOT related to "TO DO" or "TO BE" as they are covered under construction 1 and construction 2



-----------------------
1 * if you have than/as + subject + FORM OF "TO BE" as the second half of a comparison, then you must have another form of "to be" in the first half of the comparison.
or, there should be something in the first half that would make sense with "to be" in front of it.

2 * if you have than/as + subject + HELPING VERB as the second half of a comparison, you can have just about any other form of the same verb in the first part, as determined by context.

3 * if you have than/as + subject + FORM OF "TO DO" as the second half of a comparison, then you must have an ACTION VERB[/b] (or another form of "to do") in the first half of the comparison.

[Sage Pearce-Higgins]

I presume by 'helping verbs' Ron's talking about what I know as modal verbs: can, should, will, must, etc.