|
Author |
Message |
|
Manager
Joined: 07 Jan 2008
Posts: 88
Followers: 2
Kudos [?]:
15
[0], given: 1
|
If it took a bus 4 hours to get from town A to town B, what was the average speed of the bus for the trip? (1) In the first 2 hours the bus covered 100 miles. (2) The average speed of the bus for the first half of the distance was twice its average speed for the second half. Source: GMAT Club Tests - hardest GMAT questions
|
|
|
|
|
|
|
|
|
Intern
Joined: 18 Jan 2010
Posts: 18
Followers: 0
Kudos [?]:
6
[1] , given: 20
|
1
This post received
KUDOS
We need to know the total distance to come up with the average speed.
S1 - In the first 2 hours the bus covered 100 miles - not suff as it just talks about the 1st 2 hrs and the distance travelled. In next 2 hrs distance can be 100,200,150 or anything.
S2 - The average speed of the bus for the first half of the distance was twice its speed for the second half - not sufficient .....talks about the speed was twice but still doesnt tell what the distance of the 1st half was.
Together - S2 talks about the av. speed for the 1st half of the distance but doesnt say that 1st half is 100 miles. So we cant use statement 1 to come up with the total distance.
Hence answer E.
|
|
|
|
|
|
Manager
Joined: 07 Jan 2008
Posts: 88
Followers: 2
Kudos [?]:
15
[0], given: 1
|
Can't the first two hours i.e. 100 miles be the first part of the distance which can be used along with (2) to find the average speed? I am surprised at the official answer.
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[0], given: 19
|
topmbaseeker wrote: It took the bus 4 hours to get from town A to town B. What was the average speed of the bus for the trip?
1. In the first 2 hours the bus covered 100 miles
2. The average speed of the bus for the first half of the distance was twice its speed for the second half
(C) 2008 GMAT Club - m16#8 1: what about the second 2 hours? nsf. 2: ok, avg. speed for the first half (i.e. half of the total distance) was twice the speed for the second half. but what is the spped? nsf.. togather: first half speed = 100 miles/2 hrs = 100 mph. second half speed = 200 mph (from st. 2) so total distance = distance in first 2 hours + distance in second 2 hours = 200+400 = 600 miles avg. speed = 600/4 = 150 mph So C.
_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html
GT
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[0], given: 19
|
topmbaseeker wrote: Can't the first two hours i.e. 100 miles be the first part of the distance which can be used along with (2) to find the average speed? I am surprised at the official answer. Thats not correct. we do not know the speed of the bus for the second 2 hours. It could be 100mph or 200 mph or 300 mph.
_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html
GT
|
|
|
|
|
|
Manager
Joined: 07 Jan 2008
Posts: 88
Followers: 2
Kudos [?]:
15
[0], given: 1
|
But you have (1) which will give you the speed for the first 2 hours. I also choose C but the official answer is E.
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[0], given: 19
|
topmbaseeker wrote: But you have (1) which will give you the speed for the first 2 hours. I also choose C but the official answer is E. I would like to know OE. Do not see any reason that E is the OA.
_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html
GT
|
|
|
|
|
|
SVP
Joined: 17 Jun 2008
Posts: 1593
Followers: 7
Kudos [?]:
131
[0], given: 0
|
E is right. It is required to know the average speed of the first half or of second half of distance. Stmt1 does not help obtain this. Stmt1 simply tells that the bus travelled a distance of 100 miles in two hours.
|
|
|
|
|
|
Manager
Joined: 07 Jan 2008
Posts: 88
Followers: 2
Kudos [?]:
15
[0], given: 1
|
Why can't statement 1 give you average speed?
d = r t
100 = r * 2
therefore r = 50.
I still feel that the ans should be C
|
|
|
|
|
|
CEO
Joined: 29 Aug 2007
Posts: 2530
Followers: 41
Kudos [?]:
358
[0], given: 19
|
scthakur wrote: E is right. It is required to know the average speed of the first half or of second half of distance. Stmt1 does not help obtain this. Stmt1 simply tells that the bus travelled a distance of 100 miles in two hours. I think scthakur got it that I missed. Statement 1 talks about the first two hours. Statement 2 talkes about the average speeds of the bus for the first half and second half of the distance. St1 and 2 are talking entirely two different things. so Agree with E. topmbaseeker wrote: It took the bus 4 hours to get from town A to town B. What was the average speed of the bus for the trip?
1. In the first 2 hours the bus covered 100 miles
2. The average speed of the bus for the first half of the distance was twice its speed for the second half
(C) 2008 GMAT Club - m16#8
_________________
Verbal: new-to-the-verbal-forum-please-read-this-first-77546.html
Math: new-to-the-math-forum-please-read-this-first-77764.html
Gmat: everything-you-need-to-prepare-for-the-gmat-revised-77983.html
GT
|
|
|
|
|
|
Intern
Joined: 29 Nov 2008
Posts: 4
Followers: 0
Kudos [?]:
0
[0], given: 0
|
I choose C for this question.
As the distance from A to B is divided into two equal parts. So I call the speed and time to travel the 1st half of the road are S1, T1 respectively. The speed and time for second half are S2, T2. We have s1*t1 = s2*t2
We have these following equations:
T1+T2 = 4
S1= 2 S2 ( the second statement) => t2= 1/2 t1 (equal distances)
=> t1 = 4/3(h) t2 = 8/3(h)
Then use statement 1: 100 = 4/3*s1 + 2/3* s2 ( statement 1 : 100 miles for 2h)
s1= 2 s2
s1= 60 , s2 =30
=> AB = 160 (miles) => average speed = 40(mph)
Am I right???
|
|
|
|
|
|
Intern
Joined: 12 Jul 2009
Posts: 13
Followers: 0
Kudos [?]:
2
[0], given: 2
|
It has to be E.
Statement 1 misses what is 100 miles.It can be half, 2/3rd or any part of the total distance. Hence, total distance is unknown.
Statement 2 misses to replace the variables of time, speed and distance in correct form.
Both statement lack the purpose due to the same logic as in statement 1.
|
|
|
|
|
|
Manager
Joined: 24 Jul 2009
Posts: 197
Location: Anchorage, AK
Schools: Mellon, USC, MIT, UCLA, NSCU
Followers: 4
Kudos [?]:
17
[0], given: 10
|
This was a good practice problem. I struggled between C and E and can't really say that I chose either. C was the most bothersome though because on the surface it appears that you can obtain relevant numbers for the second part of the trip. However, since the rate and distance isn't explicit, one should call the statements as presented-insufficient. Posted from my mobile device 
_________________
Reward wisdom with kudos. 
|
|
|
|
|
|
Current Student
Affiliations: CFA
Joined: 21 Dec 2008
Posts: 384
Location: United States (NY)
Schools: Columbia - Class of 2013
GMAT 1: 710 Q45 V43
GMAT 2: 760 Q49 V45
Followers: 21
Kudos [?]:
96
[0], given: 61
|
topmbaseeker wrote: It took the bus 4 hours to get from town A to town B. What was the average speed of the bus for the trip? 1. In the first 2 hours the bus covered 100 miles 2. The average speed of the bus for the first half of the distance was twice its speed for the second half Source: GMAT Club Tests - hardest GMAT questions Very tricky wording. Notice that S2 says "the average speed of the bus for the first half of the distance was twice its speed for the second half. So just because S1 gives us the first half of the trip, we don't know the total distance so we don't know that the first half of the trip time-wise is the same as the first half of the trip distance-wise. Accordingly, we can't speak to the average speed or distance during the second two hours; E.
_________________
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Intern
Joined: 08 Jul 2009
Posts: 8
Followers: 0
Kudos [?]:
0
[0], given: 0
|
just to make it clearer, I'll point out the flaw in huuminh2211's equations.
he says:
"Then use statement 1: 100 = 4/3*s1 + 2/3* s2 ( statement 1 : 100 miles for 2h)
s1= 2 s2"
Although s2 is the "average" speed for the second half of the trip, it is not necessarily the average speed for any part of it. so using average speed for distance covered from time=4/3 hours till time=2 hours is not necessarily s2.
otherwise, huuminh2211's equations are all right.
|
|
|
|
|
|
Intern
Joined: 28 Jan 2010
Posts: 3
Followers: 0
Kudos [?]:
0
[0], given: 0
|
1. 100 miles in 2 hrs does not give any more information about total distance -- Not Sufficient
2. avg speed of ( 1/2 distance) = 2 avg speed of (second half distance) -- Not Sufficient.
Together, we still don't know the total distance traveled in 4 hrs. so answer is E.
|
|
|
|
|
|
CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2759
Location: Malaysia
Concentration: Marketing, Entrepreneurship
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Followers: 124
Kudos [?]:
637
[0], given: 221
|
IMO its E 1. Its not sufficient as its just giving us information for the first 2 hours, with no information of the speed being constant or varying. 2. This is also not sufficient. Take Avg speed = total dist/total time = \frac{2d}{t1+t2} ---1 T = t1+ t2 = \frac{d}{2x} + \frac{d}{x}=> 4 = \frac{3d}{2x} ----2 from equation 1 and 2 we can conclude we dont have value of X. Thus not sufficient and ans is E
_________________
Fight for your dreams :For all those who fear from Verbal- lets give it a fight
Money Saved is the Money Earned 
Jo Bole So Nihaal , Sat Shri Akaal
 Support GMAT Club by putting a GMAT Club badge on your blog/Facebook
Find out what's new at GMAT Club - latest features and updates
Gmat test review :
670-to-710-a-long-journey-without-destination-still-happy-141642.html
|
|
|
|
|
|
Manager
Joined: 09 Jan 2010
Posts: 131
Followers: 1
Kudos [?]:
2
[0], given: 12
|
gurpreetsingh wrote: IMO its E
1. Its not sufficient as its just giving us information for the first 2 hours, with no information of the speed being constant or varying.
2. This is also not sufficient.
Take Avg speed = total dist/total time = \frac{2d}{t1+t2} ---1
T = t1+ t2 = \frac{d}{2x} + \frac{d}{x}
=> 4 =\frac{3d}{2x} ----2
from equation 1 and 2 we can conclude we dont have value of X.
Thus not sufficient and ans is E hi gurpreet can u pls explain how can u consider that in the second half he covered the same distance....i.e d....
|
|
|
|
|
|
CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2759
Location: Malaysia
Concentration: Marketing, Entrepreneurship
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Followers: 124
Kudos [?]:
637
[0], given: 221
|
topmbaseeker wrote: It took the bus 4 hours to get from town A to town B. What was the average speed of the bus for the trip? 1. In the first 2 hours the bus covered 100 miles 2. The average speed of the bus for the first half of the distance was twice its speed for the second half Source: GMAT Club Tests - hardest GMAT questions Shalu pls read the statement 2 again.. avg speed of 1st half = twice of second half..that means distance same taken for the calculation.
_________________
Fight for your dreams :For all those who fear from Verbal- lets give it a fight
Money Saved is the Money Earned
Jo Bole So Nihaal , Sat Shri Akaal
Support GMAT Club by putting a GMAT Club badge on your blog/Facebook
Find out what's new at GMAT Club - latest features and updates
Gmat test review :
670-to-710-a-long-journey-without-destination-still-happy-141642.html
|
|
|
|
|
|
Intern
Joined: 27 Jan 2010
Posts: 31
Followers: 0
Kudos [?]:
5
[0], given: 0
|
I strongly feel the distance in the first half and second half cannot be the same.
Eg:
We know the total time = 4 Hrs
Say Speed 1 = 100m/h , then as per Stmt 2, Speed 2 = 50 m/h
Time1 = 2 Hrs Time2 = 2 Hrs
Distance1 = 200Miles Distance2 = 100 Miles
So there is no way the distances can be equal.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
close
