Rock samples taken from the remains of an asteroid about twice the

Hello Everyone!

Let's tackle this question, one thing at a time, and narrow it down to the correct choice quickly! Here is the original question, with the major differences between each option highlighted in orange:

Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

(A) has been dated to be 3.47 billion years old and thus is
(B) has been dated at 3.47 billion years old and thus
(C) have been dated to be 3.47 billion years old and thus are
(D) have been dated as being 3.47 billion years old and thus
(E) have been dated at 3.47 billion years old and thus are

After a quick glance over the options, there are a few places we can focus on to narrow down our choices:

1. has been vs. have been (Subject-Verb Agreement)
2. dated to be / at / as being (Idioms)
3. thus is / thus / thus are (Subject-Verb Agreement / Meaning)

Let's start with #1 on our list because it will eliminate 2-3 options right away. This is a matter of subject-verb agreement! If we look closely at the original sentence, we can find the subject:

Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

We see that the subject "rock samples" is plural, which means we need to use a plural verb to match:

(A) has been dated to be 3.47 billion years old and thus is
(B) has been dated at 3.47 billion years old and thus
(C) have been dated to be 3.47 billion years old and thus are
(D) have been dated as being 3.47 billion years old and thus
(E) have been dated at 3.47 billion years old and thus are

We can eliminate options A & B because they use a singular verb with a plural subject, which doesn't match.

Now that we have it narrowed down to only 3 options, let's tackle #2 on our list: idiom structure. Whenever we say that an item is "dated" a certain age, there is a particular way to word it. We typically say that something is "dated at" a certain age! Let's take a closer look:

(C) have been dated to be 3.47 billion years old and thus are --> not idiomatically correct = WRONG
(D) have been dated as being 3.47 billion years old and thus --> not idiomatically correct = WRONG
(E) have been dated at 3.47 billion years old and thus are --> idiomatically correct = CORRECT


There you have it - option E is the correct choice! It's the only one that uses proper subject-verb agreement and proper idiom formatting!


Don't study for the GMAT. Train for it.

Dear Friends,

Here is a detailed explanation to this question-

Concepts tested here: Subject-Verb Agreement + Idioms

• “dated at” is a correct, idiomatic construction.

A: This answer choice incorrectly refers to the plural noun “samples” with the singular verbs “has been dated” and “is”. Further, Option A incorrectly uses the unidiomatic construction “dated to be” rather than the idiomatic construction “dated at”; please remember, “dated at” is a correct, idiomatic construction.

B: This answer choice incorrectly refers to the plural noun “samples” with the singular verb “has been dated”. Further, Option B fails to form a complete sentence, as there is no active verb to act upon the subject “samples” in the latter part of the sentence – “thus evidence of the earliest known asteroid impact on Earth”.

C: This answer choice incorrectly uses the unidiomatic construction “dated to be” rather than the idiomatic construction “dated at”; please remember, “dated at” is a correct, idiomatic construction.

D: This answer choice incorrectly uses the unidiomatic construction “dated as being” rather than the idiomatic construction “dated at”; please remember, “dated at” is a correct, idiomatic construction. Further, Option D fails to form a complete sentence, as there is no active verb to act upon the subject “samples” in the latter part of the sentence – “thus evidence of the earliest known asteroid impact on Earth”.

E: Correct. This answer choice correctly refers to the plural noun “samples” with the plural verbs “have been” and “are”. Further, Option E acts upon the independent noun “samples” with the active verb “are” to form a complete thought, leading to a complete sentence. Additionally, Option E correctly uses the idiomatic construction “dated at”.

Hence, E is the best answer choice.

All the best!
Experts' Global Team

Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

(A) has been dated to be 3.47 billion years old and thus is
(B) has been dated at 3.47 billion years old and thus
(C) have been dated to be 3.47 billion years old and thus are
(D) have been dated as being 3.47 billion years old and thus
(E) have been dated at 3.47 billion years old and thus are

All part in red are wrong with respect to idioms and subject verb agreement. E is correct. Hope this helps..!!

This is what Ron Purewal of Manhattan GMAT has to say about estimated at/to be scenario
Shouldn't the same logic apply to dated at/dated to be as well?

As rightly written by @Archillees - SV Agreement error >

Also to note is Difference between C and E
C uses subjunctive form - "to be" which is not required here.
E uses correct idiom "dated at"

Hey,
"to be" is neither used as a command subjunctive nor used as a hypothetical subjunctive.
For them you need special command verbs like demand, order, require etc.
They are popularly known as "bossy verbs"
Hypothetical subjunctive, as the name suggests, uses hypothetical constructions such as "were", "would" etc.

Souvik

Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

The modifier in bold red it modifying - remains of asteroid or asteroid. Also is this modified "adjective phase". If so should it have a comma before it or not?

Hi,

Note that the highlighted portion doesn’t entirely consist of a single modifier.

I suggest you analyze the sentence structure to understand the role played by each element.

• Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid

o that eradicated the dinosaurs
• has been dated to be 3.47 billion years old and
• thus is evidence of the earliest known asteroid impact on Earth.

The highlighted modifier presents a comparison with another “asteroid”.

So it would be logical to presume that the entire modifier is modifying “asteroid”, not “remains”.

Since this modifier is used to modify a noun, we can call it a “Noun Modifier”.

Observe that the modifier is in the non-underlined portion of the official sentence and so it should be correct as such.

Of course, enclosing it in a comma pair won’t make it incorrect. However, it would be unnecessary.

Hope this helps!

Regards,
Krishna

I'm studying with the 2015 Official Guide and the very last question (#140) of the sentence correction section is this:

Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

the correct answer was "have been dated at 3.47 billion years old and thus are."

I've always thought of this phrase to be "dated to be XXX years old." For anyone who's seen similar questions, does GMAT treat "dated at" as the correct idiom at all times?

(There is a similar question that uses the word "estimated," but this one states "estimated to be XYZ years old" to be the correct answer. )

Dear daysandhours,
I'm happy to respond.

The idiom "dated at" is 100% correct and favored by the GMAT, whereas "dated to be" is awkward and unidiomatic. I discuss this in this blog:
https://magoosh.com/gmat/2013/gmat-prep ... potpourri/

You may find helpful our free GMAT Idiom ebook:
https://magoosh.com/gmat/2013/gmat-idiom-ebook/
This information is also available in free Flash Card form:
https://gmat.magoosh.com/flashcards/idioms

Does all this make sense?
Mike

GMAT likes "dated at" but "estimated to be"
GMAT is annoying at times.

Hi! estimated to be and dated at are both separate and correct idioms.

I'm happy to jump in here. Yes, as EducationAisle, the idioms "dated at" and "estimate X to be" are 100% valid GMAT idioms. These and many more are included in our free GMAT Idiom Flashcards.
https://gmat.magoosh.com/flashcards/idioms
Enjoy!
Mike

Hi Experts,

Could you please provide your comments for option C and option E.

Dated to be vs Dated at

Thanks

PathFinder007, this difference seems to have been discussed a good deal in the thread. Do you have a specific question about it?

The short answer is that "dated to be" doesn't work. We estimate/believe/prove something "to be" a certain age, but that doesn't work with "date." You could say "I estimate that this rock is 3 billion years old." You couldn't say "I date that this rock is 3 billion years old." It just isn't the same kind of verb. Similarly, you can say "I estimate it to be 3 billion years old" and not "I date it to be 3 billion years old."

First Glance

The underline starts with the verb has; other answers start with have, so look for subject-verb issues.

Issues

(1) Subject-Verb; has; is

In the original sentence, the subject is the plural rock samples and the verb is the singular has been dated. Mismatch!

A plural subject needs a plural verb; eliminate answers (A) & (B), which both use the singular has. It turns out that the sentence also contains a second verb that goes with the same plural subject: is. Only answer (A) contains this error. The remaining answer use either the plural are or eliminate the verb entirely. (Remember that split for later.)

(2) Idiom: dated to be; dated as being

If you know the correct idiom, you might spot the error in the original sentence. If you don't, a vertical scan reveals that the answers offer three different options: dated to be, dated at, or dated as being.

The correct idiom for estimating the age of something is dated at a certain age. Eliminate answers (A), (C), and (D).

(3) Structure

Tackle the are versus nothing split mentioned in the subject-verb discussion above. (Remember that you already eliminated answer (A) for using is.)

(B), (D): Rock samples have been dated and thus evidence
(C), (E): Rock samples have been dated and thus are evidence

The and creates a parallel construction. Answers (B) and (D) are missing the needed verb are and are therefore sentence fragments; eliminate them

The Correct Answer

Correct answer (E) changes both verbs to the plural form to match the plural subject rock samples. Further, this choice uses the correct idiom, dated at a certain age.

Do refer the excerpt from Manhattan Sentence Correction Sixth Edition.