The same amount of acreage PRODUCES twice as many apples as it DID in 1910.

The simple tense forms of to do are does, do and did.
One purpose of does, do and did is to STAND IN for the simple tense forms of an ANTECEDENT VERB.
The antecedent verb can be in virtually any tense.
Here, did serves to stand in for the simple past tense form of the antecedent verb produces.
In other words:
did = produced.
Conveyed meaning:
The same amount of acreage PRODUCES twice as many apples as it PRODUCED in 1910.

Thanks Guru for your prompt reply, but I'm still confused regarding that particular point

in the Manhattan SC book page 249 we have:

The first instance of the verb should usually match the helping verb in tense. If you
change tenses, repeat the whole verb in the new tense.

Wrong: I have never seen an aardvark, but last year my father did.
Right: I have never seen an aardvark, but last year my father saw one.

So according to this rule the correct form of the sentence et the one you wrote earlier
The same amount of acreage PRODUCES twice as many apples as it PRODUCED in 1910.


the book also stated:

In the rare cases in which the tenses do not need to match, the exact verb form missing after the helping verb should be present elsewhere in the sentence.
Wrong: Our cars were designed to inspire envy, and they ARE.
Right: Our cars were designed to inspire envy, and they do

Many thanks in advance[/u]

Amadalia wrote: So according to this rule the correct form of the sentence et the one you wrote earlier
The same amount of acreage PRODUCES twice as many apples as it PRODUCED in 1910.

Typically, the GMAT uses does/do/did in the context of a COMPARISON.
In most cases, there is no ellipsis: the purpose of does/do/did is to serve not as a helping verb but as a SUBSTITUTE for an antecedent verb.
The antecedent verb and does/do/did can be in different forms.
Consider the following OA to an SC from GMAT Prep:
Since 1990 the global economy HAS GROWN more than it DID during the 10000 years from the beginning of agriculture to 1950.
Here, DID serves as a substitute for the simple past tense form of HAS GROWN.
Conveyed meaning:
Since 1990 the global economy HAS GROWN more than it GREW during the 10000 years from the beginning of agriculture to 1950.
Notice that did and its antecedent verb -- has grown -- are in different forms.
Implication:
On the GMAT, does/do/did and its antecedent verb can be in different forms.

Wrong: Our cars were designed to inspire envy, and they ARE.

Implied meaning:
Our cars were designed to inspire envy, and they are [inspiring envy].
Here, the participle in brackets -- inspiring -- has been omitted.
A PARTICIPLE may be omitted only if it appears in the same form earlier in the sentence.
In the sentence above, inspiring does not appear in the first clause; hence, it cannot be omitted from the second clause.
Result:
The omission of inspiring constitutes a clear error.

Thanks a million Guru !!!!
you nail it

by the way,I've just been told by some manhattan staff that this part of the book is wrong and will be removed in the next edition
Many thanks GURU

GMATGuruNY wrote:

Amadalia wrote: So according to this rule the correct form of the sentence et the one you wrote earlier
The same amount of acreage PRODUCES twice as many apples as it PRODUCED in 1910.

Typically, the GMAT uses does/do/did in the context of a COMPARISON.
In most cases, there is no ellipsis: the purpose of does/do/did is to serve not as a helping verb but as a SUBSTITUTE for an antecedent verb.
The antecedent verb and does/do/did can be in different forms.
Consider the following OA to an SC from GMAT Prep:
Since 1990 the global economy HAS GROWN more than it DID during the 10000 years from the beginning of agriculture to 1950.
Here, DID serves as a substitute for the simple past tense form of HAS GROWN.
Conveyed meaning:
Since 1990 the global economy HAS GROWN more than it GREW during the 10000 years from the beginning of agriculture to 1950.
Notice that did and its antecedent verb -- has grown -- are in different forms.
Implication:
On the GMAT, does/do/did and its antecedent verb can be in different forms.

Wrong: Our cars were designed to inspire envy, and they ARE.

Implied meaning:
Our cars were designed to inspire envy, and they are [inspiring envy].
Here, the participle in brackets -- inspiring -- has been omitted.
A PARTICIPLE may be omitted only if it appears in the same form earlier in the sentence.
In the sentence above, inspiring does not appear in the first clause; hence, it cannot be omitted from the second clause.
Result:
The omission of inspiring constitutes a clear error.

Hi GMATguru,

Thanks for your brilliant post. It clarifies a lot of my doubts.

I wanted to request if you can share more information from your arsenal on verbs such as has, have, had etc. I am primarily interested in what constructions can occur when they are used as helping verbs and when they are used as main verbs.

Also how does the construction and structure differs in both usages?

Amadalia wrote:Today, because of improvements in agricultural technology, the same amount of acreage produces double the apples that it has in 1910.

(A) double the apples that it has
(B) twice as many apples as it did
(C) as much as twice the apples it has
(D) two times as many apples as there were
(E) a doubling of the apples that it did
The OA is B I still have one question about it:
(B) twice as many apples as it did [produce] (ellipsis) but this form of "produce" is nowhere in the sentence,
Many thanks in advance

Dear GMATGuru,

The amount of acreage must be compared to other amount. However OA does not have any Value to compare amounts?

Can you please clarify?

Thanks

Mo2men wrote:Dear GMATGuru,

The amount of acreage must be compared to other amount. However OA does not have any Value to compare amounts?

Can you please clarify?

Thanks

OA: Today, the same amount of acreage produces twice as many apples as it did in 1910.
The phrase in blue conveys that the amount of acreage producing apples today is the SAME as the amount that produced apples in 1910.
For example:
If 100 acres produced apples in 1910, then 100 acres are producing apples today.

Today, because of improvements in agricultural technology, the same amount of acreage produces double the apples that it has in 1910.
It has in present perfect tense but the action happened in the past hence incorrect.
Double could be associated with a number or a figure but not apples.

(A) double the apples that it has

(B) twice as many apples as it did
This is correct answer choice.

(C) as much as twice the apples it has
This is incorrect because of the it has wording

(D) two times as many apples as there were
There is ambiguous.

(E) a doubling of the apples that it did
A doubling of apples is a noun and cant be used.