Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 21 Oct 2016, 06:15

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If Car X followed Car Y across a certain bridge that is 1/2

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 35240
Followers: 6618

Kudos [?]: 85292 [4] , given: 10236

If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

13 Aug 2012, 07:09
4
KUDOS
Expert's post
10
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

79% (02:06) correct 21% (01:02) wrong based on 929 sessions

### HideShow timer Statistics

If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

(1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Car Y drove off the bridge.
(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.

Practice Questions
Question: 16
Page: 276
Difficulty: 600
[Reveal] Spoiler: OA

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 35240
Followers: 6618

Kudos [?]: 85292 [3] , given: 10236

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

17 Aug 2012, 01:32
3
KUDOS
Expert's post
12
This post was
BOOKMARKED
SOLUTION

If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

Let the time needed for car X to travel across the bridge be $$t_x$$ seconds and the time needed for car Y be $$t_y$$ seconds.

(1) Car X drove onto the bridge exactly 3 seconds after car Y drove onto the bridge and drove off the bridge exactly 2 seconds after car Y drove off the bridge --> car X needs 1 second less to travel across the bridge than car Y --> $$t_y=t_x+1$$. Not sufficient to calculate $$t_x$$.

(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour. 30 miles per hour is $$\frac{30}{3600}=\frac{1}{120}$$ miles per second --> car Y needs $$t_y=\frac{(\frac{1}{2})}{(\frac{1}{120})}=60$$ seconds to travel across the bridge. Not sufficient to calculate $$t_x$$.

(1)+(2) $$t_y=t_x+1$$ and $$t_y=60$$ --> $$t_x=60-1=59$$. Sufficient.

_________________
Manager
Joined: 02 Nov 2009
Posts: 138
Followers: 2

Kudos [?]: 150 [0], given: 97

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

16 Sep 2012, 21:43
Bunuel

Can this not be vvorked out just vvith A

--> since distances are equal
then equate

SX. Tx = Sy. Ty

Is this not possible

then in that case statement 1 becomes sufficient please explain

Bunuel wrote:
SOLUTION

If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

Let the time needed for car X to travel across the bridge be $$t_x$$ seconds and the time needed for car Y be $$t_y$$ seconds.

(1) Car X drove onto the bridge exactly 3 seconds after car Y drove onto the bridge and drove off the bridge exactly 2 seconds after car Y drove off the bridge --> car X needs 1 second less to travel across the bridge than car Y --> $$t_y=t_x+1$$. Not sufficient to calculate $$t_x$$.

(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour. 30 miles per hour is $$\frac{30}{3600}=\frac{1}{120}$$ miles per second --> car Y needs $$t_y=\frac{(\frac{1}{2})}{(\frac{1}{120})}=60$$ seconds to travel across the bridge. Not sufficient to calculate $$t_x$$.

(1)+(2) $$t_y=t_x+1$$ and $$t_y=60$$ --> $$t_x=60-1=59$$. Sufficient.

Director
Affiliations: SAE
Joined: 11 Jul 2012
Posts: 509
Location: India
Concentration: Strategy, Social Entrepreneurship
GMAT 1: 710 Q49 V37
GPA: 3.5
WE: Project Management (Energy and Utilities)
Followers: 43

Kudos [?]: 228 [0], given: 269

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

16 Sep 2012, 22:48
1
This post was
BOOKMARKED
The question asks the time taken by X to cross the bridge.

How come? Statement 1 helps us to get the relationship between X and Y wrt time. It does not tell us the time taken by Y to cross

Statement 2 gives us the time taken by Y to cross the bridge.

Both the statements together are sufficient.

Hope this helps!

Question level - 600
_________________

First Attempt 710 - http://gmatclub.com/forum/first-attempt-141273.html

Manager
Joined: 17 Jul 2010
Posts: 124
Followers: 1

Kudos [?]: 42 [0], given: 43

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

02 May 2013, 20:07
Banuel,

I'm not seeing it, is there a way you can list the three or four item being tested? and what makes the answer sufficient?

Time?
Rate of Speed?
Distance?
Any other?

Thanks.
Math Expert
Joined: 02 Sep 2009
Posts: 35240
Followers: 6618

Kudos [?]: 85292 [0], given: 10236

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

03 May 2013, 03:52
laythesmack23 wrote:
Banuel,

I'm not seeing it, is there a way you can list the three or four item being tested? and what makes the answer sufficient?

Time?
Rate of Speed?
Distance?
Any other?

Thanks.

Not sure I understand what you mean...

Anyway, we need to get $$t_x$$.

From (1) we have that $$t_y=t_x+1$$ and from (2) we have that $$t_y=60$$, thus $$t_x=60-1=59$$.
_________________
Senior Manager
Joined: 21 Jan 2010
Posts: 344
Followers: 2

Kudos [?]: 163 [0], given: 12

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

03 May 2013, 16:43
In such questions, i look at the short concise option 1st. I look at B and it doesn't talk about one of the two cars. Eliminate answer choice B and D. Now look at A, it gives a relation between time.
We can form two eqn for two cars using speed distance formulae. For 1st car assume all capital letters for its calculations.
S= D/T
For 2nd car , assume small letters:
s=D/t

Now we know that t=T-1 since it took one sec less to travel the bridge.
We also know the length of the bridge. However we don't know the speeds of time in absolute numbers to determine the answer. So we can't get anywhere with the 2Eqns.

Now add info from B and we can compute our answer. hence C.
Manager
Joined: 17 Jul 2010
Posts: 124
Followers: 1

Kudos [?]: 42 [0], given: 43

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

07 May 2013, 06:18
Bunuel wrote:
laythesmack23 wrote:
Banuel,

I'm not seeing it, is there a way you can list the three or four item being tested? and what makes the answer sufficient?

Time?
Rate of Speed?
Distance?
Any other?

Thanks.

Not sure I understand what you mean...

Anyway, we need to get $$t_x$$.

From (1) we have that $$t_y=t_x+1$$ and from (2) we have that $$t_y=60$$, thus $$t_x=60-1=59$$.

The concept being tested here is RTD right?
Manager
Joined: 24 Apr 2013
Posts: 54
Schools: Duke '16
Followers: 0

Kudos [?]: 9 [0], given: 76

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

07 May 2013, 14:05
I dont know if i am wrong but all i did was use the formula speed = distance x time and they have given us both speed ie the rate traveled and the time so am i wrong?
Math Expert
Joined: 02 Sep 2009
Posts: 35240
Followers: 6618

Kudos [?]: 85292 [0], given: 10236

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

08 May 2013, 06:04
I dont know if i am wrong but all i did was use the formula speed = distance x time and they have given us both speed ie the rate traveled and the time so am i wrong?

The formula is (speed)*(time)=(distance).
_________________
Math Expert
Joined: 02 Sep 2009
Posts: 35240
Followers: 6618

Kudos [?]: 85292 [0], given: 10236

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

08 May 2013, 06:05
laythesmack23 wrote:
Bunuel wrote:
laythesmack23 wrote:
Banuel,

I'm not seeing it, is there a way you can list the three or four item being tested? and what makes the answer sufficient?

Time?
Rate of Speed?
Distance?
Any other?

Thanks.

Not sure I understand what you mean...

Anyway, we need to get $$t_x$$.

From (1) we have that $$t_y=t_x+1$$ and from (2) we have that $$t_y=60$$, thus $$t_x=60-1=59$$.

The concept being tested here is RTD right?

Yes, that's correct.
_________________
Senior Manager
Joined: 13 May 2013
Posts: 472
Followers: 3

Kudos [?]: 146 [1] , given: 134

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

30 Jul 2013, 16:28
1
KUDOS
1
This post was
BOOKMARKED
If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

(1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Car Y drove off the bridge.
We don't know how long Car Y was on the bridge for. Therefore, we don't know how long Car X was on the bridge for.
INSUFFICIENT

(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.
This tells us nothing about Car X.
INSUFFICIENT

1+2)
If the bridge is 1/2 mile long and Car Y crossed it at 30MPH it would have taken exactly one minute to cross the bridge. If Car X followed behind Car Y by 3 seconds and left the bridge just two seconds after Y it gained one second on Y. Therefore, Car X crossed the bridge in 29 seconds.
SUFFICIENT

(C)
Intern
Joined: 25 Sep 2013
Posts: 5
Followers: 0

Kudos [?]: 0 [0], given: 13

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

12 Jan 2014, 13:55
WholeLottaLove wrote:
If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

(1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Car Y drove off the bridge.
We don't know how long Car Y was on the bridge for. Therefore, we don't know how long Car X was on the bridge for.
INSUFFICIENT

(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.
This tells us nothing about Car X.
INSUFFICIENT

1+2)
If the bridge is 1/2 mile long and Car Y crossed it at 30MPH it would have taken exactly one minute to cross the bridge. If Car X followed behind Car Y by 3 seconds and left the bridge just two seconds after Y it gained one second on Y. Therefore, Car X crossed the bridge in 29 seconds.
SUFFICIENT

(C)

I think you mean 59 seconds. If it took one minute for Car Y to cross and Car X gained on Car Y by one second then the time it took would be 59 seconds.
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 12146
Followers: 538

Kudos [?]: 151 [0], given: 0

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

28 Apr 2015, 07:55
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 12146
Followers: 538

Kudos [?]: 151 [0], given: 0

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

21 May 2016, 21:30
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Senior Manager
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 293
Followers: 16

Kudos [?]: 76 [0], given: 2

Re: If Car X followed Car Y across a certain bridge that is 1/2 [#permalink]

### Show Tags

30 Jul 2016, 08:38
Bunuel wrote:
If Car X followed Car Y across a certain bridge that is 1/2 mile long, how many seconds did it take Car X to travel across the bridge?

(1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Car Y drove off the bridge.
(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.

We are given that Car X follows Car Y across a bridge that is ½ mile long. We need to determine the time, in seconds, it took Car X to travel the ½ mile across the bridge.

Statement One Alone:

Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and drove off the bridge exactly 2 seconds after Car Y drove off the bridge.

From statement one, we know that Car X gained 1 second on Car Y while the two cars traveled over the bridge. Thus, Car X took 1 second less than Car Y took to cross the bridge. However, without knowing the actual time it took Car Y to cross the bridge, we still don't know the number of seconds it took Car X to cross it. Statement one alone is insufficient to answer the question. We can eliminate answer choices A and D.

Statement Two Alone:

Car Y traveled across the bridge at a constant speed of 30 miles per hour.

From statement two we can determine the time it took Car Y to cross the bridge.

time = distance/rate

time = (1/2)/30

time = 1/60 hour

Since 1 hour = 3,600 seconds, 1/60 hour = 3,600 x 1/60 = 60 seconds.

We know that Car Y took 60 seconds to travel across the bridge. However, we do not know anything about Car X, so statement two is insufficient to answer the question. We can eliminate answer choice B.

Statements One and Two Together:

Because we know that that Car Y took 60 seconds to travel across the bridge and Car X took 1 second less, we know that it took Car X 59 seconds to travel across the bridge.

_________________

Jeffrey Miller
Jeffrey Miller

Re: If Car X followed Car Y across a certain bridge that is 1/2   [#permalink] 30 Jul 2016, 08:38
Similar topics Replies Last post
Similar
Topics:
A car fleet holds two car models, X and Y. Of the cars in the car flee 1 19 Sep 2016, 05:28
1 If the ratio of brown cars to blue cars in a certain parking lot is 2: 4 25 Jul 2016, 10:10
31 While on a straight road, Car X and Car Y are traveling at 12 17 Mar 2012, 18:44
3 A certain group of car dealerships agreed to donate x dollar 12 21 Feb 2011, 01:36
1 If car X followed car Y across a certain bridge that is 21-m 4 09 Oct 2010, 13:13
Display posts from previous: Sort by