BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

sharp-edged flakes

Expert replies
Post new topic Locked
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members
Thanked: 237 times
GMAT Score:730
by logitech » Mon Feb 02, 2009 3:04 pm
scientist have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date /when it is known that humans make/ stone tools



when is is known that humans make
at which it is known that human had made
at which humans are known to have made
that humans are known to be making
of humans who were known to make.

I need someone to explain the options. Thanks,
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Sentence Correction |
Master | Next Rank: 500 Posts
Posts: 189
Joined: Tue Sep 16, 2008 10:42 amFollowed by: 1 member
Thanked: 11 times

by hitmewithgmat » Mon Feb 02, 2009 4:45 pm
I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 130
Joined: Sat Dec 29, 2007 5:35 am
Location: SGP
Thanked: 5 times

Re: sharp-edged flakes

by satish.nagdev » Mon Feb 02, 2009 10:44 pm
logitech wrote:scientist have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.60 million years ago, pushing back by more than 150,000 years the earliest date /when it is known that humans make/ stone tools



when is is known that humans make
at which it is known that human had made
at which humans are known to have made
that humans are known to be making
of humans who were known to make.

I need someone to explain the options. Thanks,
I Think it is B
as per [between 2.52 and 2.60 million years ago, pushing back by more than 150,000 ] humans made stones somewhere around say 2.52mn - 150000 so that period existed before 2.52 mn hence we need "had"

Correct me if i'm wrong.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 1159
Joined: Wed Apr 16, 2008 10:35 pm
Thanked: 56 times

by raunekk » Tue Feb 03, 2009 1:24 am
i will go with C..

we need present perfect..

stone tools made in past are still there...

OA??
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 28
Joined: Sun Feb 01, 2009 10:40 am
Location: Toronto

by dimonya » Tue Feb 03, 2009 11:10 am
lol i would say that the answer is actually D....

here is why:

1. the reason for the highlighted area of the sentence is to to clarify to the reader what date the passage is referring to


2. to make the clarification author introduces characteristics of that date: i) presently we know that humans were making tools at that time ii) they were making tools at that time and continued as time propagated into the future


C says that the action has been completed => they were not making tools anymore => not true

B similar to C

E date is not one of the characteristics of the humans :)

A we are not referring to a point in time here but to a date which corresponds to that point in time

OA=?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 727
Joined: Sun Jun 08, 2008 9:32 pmFollowed by: 1 member
Thanked: 8 times

by umaa » Tue Feb 03, 2009 11:57 am
IMO E.

A and B - IT reference is wrong.

C - Present tense. Do humans know how to make stone tools now?

D - THAT is not relevant here

E - correct answer. Uses simple past tense.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 139
Joined: Wed Oct 22, 2008 4:36 am
Thanked: 17 times

by sacx » Tue Feb 03, 2009 12:44 pm
I will go for C

For sentences with comma the best way to find an answer is to put the part of the sentence following the comma at the start of the sentence

Pushing back by more than 150,000 years the earliest date at which humans are known to have made stone tools scientist have dated sharp-edged flakes of stone found in the fine-grained sediments of a dry riverbed in the Afar region of Ethiopia to between 2.52 and 2.6 million years ago

the part in bold can be ignored as it is there only to confuse you
Last edited by sacx on Tue Feb 03, 2009 10:51 pm, edited 1 time in total.
SACX
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 594
Joined: Thu Aug 14, 2008 11:51 pm
Thanked: 12 times

by nervesofsteel » Tue Feb 03, 2009 10:02 pm
IMO C

when is is known that humans make<- Use of present tense is wrong
at which it is known that human had made <- Known to is right idiom..

at which humans are known to have made < -Correct use of Have made and Idiom Known to

that humans are known to be making <- Passive and use of making is wrong

of humans who were known to make. <- Dates cannot be OF HUMANS... Wrong[/b]
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members
Thanked: 237 times
GMAT Score:730

by logitech » Wed Feb 04, 2009 12:13 pm
OA C
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members
Thanked: 237 times
GMAT Score:730

by logitech » Wed Feb 04, 2009 12:19 pm
hitmewithgmat wrote:I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.
You rock dude! Thanks for the detailed explanation. I really appreciate it.
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 189
Joined: Tue Sep 16, 2008 10:42 amFollowed by: 1 member
Thanked: 11 times

no problem.

by hitmewithgmat » Wed Feb 04, 2009 2:14 pm
No problem Logitech!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 59
Joined: Tue Jun 10, 2008 6:49 pm
Thanked: 2 times

by cartera » Wed Mar 11, 2009 7:48 am
hitmewithgmat wrote:I think the answer is C ( I Might be wrong but here is my reason).

Basically, this sentence tries to tell us that "humans are known to have make" ( this precedes millions years ago), not it is known that humans make (<--- this is wrong because it ignores time line.). To be more precise, look at the example below. ( Excerpt from Kaplan GMAT pocket reference page #210)

I am glad to meet you. ( I'm glad to be in the process of meeting you right now).

I am glad to have met you. ( I am glad now that I met you earlier today, last week, or whenever).

Anyway, this question contains IDIOM problem.

KNOWN TO

A) ....it is known that humans make - don't use "known to"idiom and it distorts the meaning of the sentence. However, I don't know whether "when" is ok to use. sorry...

B) same problem as A.

C) my answer. it perfectly fits the Idiom and "humans are known to have made"

D)...known to be making... You know this can't be an answer, right? it distorts the meaning of the sentence.

E)simply wrong because it is illogical and wordy. besides, remember, it has to use "humans are known to HAVE MADE".


I hope this helps but if the answer is not C, wow. disregard this post.
Thanks.
could you explain the difference between known to and know that?
thanks
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 232
Joined: Fri Jul 04, 2008 4:14 pmFollowed by: 1 member
Thanked: 14 times
GMAT Score:760

by rs2010 » Thu Mar 12, 2009 7:25 am
'Known that' is not correct usage.
'Known to' is correct idiom, which is a phrase whose meaning cannot be determined by the literal definition of the phrase itself, but refers instead to a figurative meaning that is known only through common use.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 59
Joined: Tue Jun 10, 2008 6:49 pm
Thanked: 2 times

by cartera » Thu Mar 12, 2009 6:21 pm
hemantsood wrote:'Known that' is not correct usage.
'Known to' is correct idiom, which is a phrase whose meaning cannot be determined by the literal definition of the phrase itself, but refers instead to a figurative meaning that is known only through common use.
I dont think Known that is an incorrect idiom:

Many - though certainly not all - of the investors who gave Madoff their money should have known that nobody has the financial chops to "opportunistically time" every purchase and get safely into treasuries every time the market drops. Even Warren Buffet ("the Oracle of Omaha") lost $25 billion last year.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Locked
• Page 1 of 1