a data from gmat club

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diebeatsthegmat: Legendary Member; Posts: 1119; Joined: Fri May 07, 2010 8:50 amFollowed by: 3 members; Thanked: 29 times

by diebeatsthegmat » Wed Jun 22, 2011 12:48 pm

i think the answer should be E
they say the speed is limited Ìƒkmh, this mean their speed could be from 1 to 70, right? and they never break that speed...thus, in conlusion the speed is always from 10 t0 70
then from 1 we can find the average speed of john and jane is 40 and 60 becase we know in 5 hours, john goes 200 kmh and jane goes 500-200= 300
but from the last distance we dont know the average speed so insufficient
statement 2 let us know about jane speed > insuficient
1+2 cant solve anything
E
how to you guy think?

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Source: Beat The GMAT — Data Sufficiency | Wed Jun 22, 2011 12:48 pm

Ashley@VeritasPrep: GMAT Instructor; Posts: 199; Joined: Tue May 17, 2011 6:06 amFollowed by: 121 members; Location: Cambridge, MA; Thanked: 192 times; GMAT Score:780

by Ashley@VeritasPrep » Wed Jun 22, 2011 1:33 pm

This is tricky, and you're on the right track (but with a mistake at the end

). You're totally right about everything you said as to why St. 1 is insufficient alone, and about the fact that St. 2 alone doesn't tell us anything about John's average speed, such that it too is insufficient.

But now let's combine. One important thing is that St. 2 gives us part of the information we were missing from St. 1 -- we now know that Jane's average speed for the WHOLE trip was 60mph, AND we know that it was 60mph for the first 300 miles, so in order to stay at an average of 60mph overall, she MUST have also averaged 60mph for the last 200 miles. So that means that that last 200 miles took here 3-and-one-third hours. Now. Here comes important fact #2, which is this "never broke the speed limit of 70mph" bit. At the time when John and Jane crossed paths, John had 300 miles to go. If he never exceeded 70mph, the SHORTEST possible time that 300 miles could have taken him (i.e. if he drove AT 70mph) would still be over 4 hours (300/7). So he can't possibly have finished by the time Jane finished 3-and-one-third hours after they crossed paths. So there's our definitive answer to the question, from the combination of Sts. 1 and 2.

Ashley Newman-Owens
GMAT Instructor
Veritas Prep

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Sun Jun 26, 2011 5:03 am

diebeatsthegmat wrote:

I received a PM asking me to comment.
I agree with Ashley.

Statements 1 and 2 combined:
Jane:
Total time = 500/60 = less than 9 hours.

John:
Minimum time for remaining 300 miles = 300/70 = over 4 hours.
Since it took John 5 hours to meet Jane, his minimum total time is over 9 hours.

Thus, Jane arrived earlier than John did.
Sufficient.

The correct answer is C.

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diebeatsthegmat: Legendary Member; Posts: 1119; Joined: Fri May 07, 2010 8:50 amFollowed by: 3 members; Thanked: 29 times

by diebeatsthegmat » Sun Jun 26, 2011 10:50 am

GMATGuruNY wrote:
diebeatsthegmat wrote:
I received a PM asking me to comment.
I agree with Ashley.

Statements 1 and 2 combined:
Jane:
Total time = 500/60 = less than 9 hours.

John:
Minimum time for remaining 300 miles = 300/70 = over 4 hours.
Since it took John 5 hours to meet Jane, his minimum total time is over 9 hours.

Thus, Jane arrived earlier than John did.
Sufficient.

really easy to understand... thank you Guru and Asley
The correct answer is C.

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rahulvsd: Master | Next Rank: 500 Posts; Posts: 184; Joined: Tue Sep 07, 2010 9:43 amFollowed by: 1 member; Thanked: 6 times

by rahulvsd » Mon Jun 27, 2011 7:05 am

Thanks a lot, Mitch. It makes sense to me now

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