The "no" above was in reference to exactly that. I don't think we'll see "estimated at" in a correct answer. However, English is tricky--it depends on the intended meaning. We certainly can't say "estimated at X years old." The idiom is "estimated to be." But what about something else? I could imagine a sentence that said "The damage was estimated at $45 million dollars." This makes more sense than "to be," since a rock sample can BE millions of years old, but damages can't BE millions of dollars. Rather, millions of dollars in damages occurred.

Having said all that, I don't have an official SC question to validate that usage for the GMAT. If anyone can find a correct official answer with ANY use of "estimated at," I'd be interested to see it.
_________________

Main Issues:

1) SV: "Samples...have"
2) Correct Idiom: "dated at"

(A) has been dated to be 3.47 billion years old and thus is - Wrong: 1) SV 2) Idiom
(B) has been dated at 3.47 billion years old and thus - Wrong: 1) SV 2) Structure
(C) have been dated to be 3.47 billion years old and thus are - Wrong: Idiom
(D) have been dated as being 3.47 billion years old and thus - Wrong: 1) Idiom 2) Structure
(E) have been dated at 3.47 billion years old and thus are - Correct

907. 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.
Meaning:
Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid = ->So some rock samples were taken. No verb for plural subject Rock Samples till now
that eradicated the dinosaur
“That” is referring to asteroid. Asteroids eradicated the dinosaur. No verb for plural subject Rock Samples till now
has been dated to be 3.47 billion years old
This is the verb for the plural subject rock samples. A singular verb has been dated. SV pair error exist.
Not eliminating on basic of any idiom usage here but “dated at” is correct. “Estimated at” and “Estimated to be” is acceptable
thus is evidence of the earliest known asteroid impact on Earth.
Again singular “is” for plural subject Rock Samples
Finally meaning,
The rock samples Has been dated … and Is evidence …
Error:

(A) has been dated to be 3.47 billion years old and thus is
Error as pointed out
(B) has been dated at 3.47 billion years old and thus
Same error as pointed out also missing verb after “thus”
(C) have been dated to be 3.47 billion years old and thus are
Seems fine. Original doubt exists on idiom “dated at vs dated to be”
(D) have been dated as being 3.47 billion years old and thus
As being is incorrect to use with dated
(E) have been dated at 3.47 billion years old and thus are
Seems fine. Original doubt exists on idiom “dated at vs dated to be”

C vs E, comes down to idiom usage only. So going by what we know “dated at “is definitely correct usage as we would have heard at many occasion.
So correct answer E.

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
Has is incorrect with “Rock samples”.
“is” is incorrect here. Requires “are”.
Correct Idiom – “Dated at”

(B) has been dated at 3.47 billion years old and thus
Has is incorrect with “Rock samples”.
Rock samples …thus evidence. Helping verb is missing.

(C) have been dated to be 3.47 billion years old and thus are
Correct Idiom – “Dated at”

(D) have been dated as being 3.47 billion years old and thus
Rock samples …thus evidence. Helping verb is missing.
Correct Idiom – “Dated at”

(E) have been dated at 3.47 billion years old and thus are
“Dated at” is the correct idiom.

OFFICIAL GMAT EXPLANATION

Agreement; Idiom

The plural subject of this sentence, Rock samples, requires plural verb phrases—have been dated and are rather than has been dated and is.The idiomatic way of expressing estimation of age is with the phrase dated at.

A The subject and verbs do not agree; dated to be … is not idiomatic.

B The subject and verb do not agree; the conjunction and thus should be followed by a verb.

C Dated to be is not idiomatic.

D As being is not idiomatic; the conjunction and thus should be followed by a verb.

E Correct. The plural verbs match the plural subject, and the wording of the sentence is idiomatic.

The correct answer is E.

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-> Subject verb agreement issue. We have "rock samples"(plural). has is incorrect.
(B) has been dated at 3.47 billion years old and thus-> Subject verb agreement issue. We have "rock samples"(plural). has is incorrect.
(C) have been dated to be 3.47 billion years old and thus are-> "dated to be" is incorrect.
(D) have been dated as being 3.47 billion years old and thus-> "as being" is incorrect.
(E) have been dated at 3.47 billion years old and thus are-> It is better.

So, I think E.

Split 1: have/has split will eliminate A and B right away. Why? The subject of the sentence is rock sampleS <-- Plural.

Split 2: to be/as being/at. 'at' is idiomatic.

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 Correct
_________________

Any other way to land to the correct option (E) apart from the idiom-based rule ?
"dated at" and "dated to be" both look correct to me, so I'm still in a dilemma to choose "dated at".

Is there any other logic behind choosing "dated at" rather than "dated to be" ?

Cheers !

Look at the plural verbs and whether they match the plural subject. The correct answer (E) shows proper match.

"Dated to be" is not idiomatic. You would need to know that "dated at" is the correct use of the idiom.

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.

V spotted:
eradicated- asteroid
taken- X
has been (S)- Rock Samples (P)
is (S) - Rock Samples (P)

(A) has been dated to be 3.47 billion years old and thus is
S1≠V1
S2≠V2

(B) has been dated at 3.47 billion years old and thus
S1≠V1
S2≠V2 (verb 2 is missing)

(C) have been dated to be 3.47 billion years old and thus are
S1=V1
S2=V2

(D) have been dated as being 3.47 billion years old and thus
S1=V1
S2≠V2 (verb 2 is missing)

(E) have been dated at 3.47 billion years old and thus are
S1=V1
S2=V2

Difference between dated to be & dated at.
Meaning of dated: to say how long something has existed on earth/ when it was made
at: is a preposition
to be: something in the future (eg: His bride to be)

Meaning of estimated: to calculate something, before you have all the facts and figures.

So, of course, for dated, you will use dated at, because the date is concreted somewhere around that time and we have a certain degree of confidence, While estimated is made, before we have confidence over the given facts. Hence, we use a preposition for dated and a futuristic verb (to-be) for estimated.


Estimated at vs Estimated to be
The crowd estimated at 14,000 - this is what has happened to Noun (here CROWD).

The crowd estimated to be 14,000 - this is what will happen to Noun (not sensible here as the crowd is already dispersed)

Dated at vs Dated to be
"dated to be" is functioning as a synonym with "estimated," which takes "to be" in its proper idiomatic construction.
"dated at" is the time at which an item has been found. It does not hav e to be exact, or accurate. Just to be in past.

Hi everyone!!!
It would be of great help if the exact difference between estimated at and estimated to be is made clear.
Thanks in advance.

Hey Prithwish093, This link made sense to me. See if it helps you.

http://gmatidioms.blogspot.com/2010/11/estimated-at-vs-estimated-to-be.html#:~:text=%22estimated%20at%22%20should%20be%20used,which%20the%20estimation%20was%20made.&text=The%20rock%20that%20the%20Z,to%20be%205000%20years%20old.

Like most things on the GMAT, this also depends on the context.

Hello experts!

I have picked this error-detection question from a renowned SAT prep website :-

Halley's comet is a potato-shaped lump (A) about ten miles long (B) with a mass (C) estimated at 10 billion tons,(D) most of which is water ice.(E)No error.

The answer to this question is E.It means that 'estimated at' properly used.I have read almost all posts but am still not convinced with the nuance of usage of these two idioms(Estimated at and Estimated to be).

souvik101990 Can you please help me out and give a conclusion on this?

This is interesting. I am reasonably sure that estimated to be is actually better.

An official sentence:

Paleontologists believe that fragments of a primate jawbone unearthed in Burma and estimated to be 40 to 44 million years old provide evidence of a crucial step along the evolutionary path that led to human beings.
_________________