If Car X followed Car Y across a certain bridge that is 1/2 mile long,

Question

GMATBusters’ Quant Quiz Question -1

If Car X followed Car Y across a certain bridge that is 1/2 mile long, what is the time when Car X pass 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 travelled across the bridge at a constant speed of 30 miles per hour

GMATBusters · Accepted Answer

If Car X followed Car Y across a certain bridge that is 1/2 mile long,  what is the time  when Car X pass 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 travelled across the bridge at a constant speed of 30 miles per hour.

Question is asking about the Time (time in Clock) but we  don't have any info regarding the time  at start/end/travel.
So, the same can not be answered even by combining both the statements, 
hence  Answer is E.

Kinshook · Answer

Asked: If Car X followed Car Y across a certain bridge that is 1/2 mile long, what is the time when Car X pass 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.
Car X takes 1 second less than car Y to pass the bridge.
Since the time taken by car Y to pass the bridge is unknown
NOT SUFFICIENT

(2) Car Y travelled across the bridge at a constant speed of 30 miles per hour 
Car Y passes the bridge in = (1/2)/30 = 1/60 hours = 1 minutes; Length of the car Y is ignored as compared to length of the bridge.
But nothing is mentioned about car X
NOT SUFFICIENT

(1) + (2) 
(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 takes 1 second less than car Y to pass the bridge.
(2) Car Y travelled across the bridge at a constant speed of 30 miles per hour 
Car Y passes the bridge in = (1/2)/30 = 1/60 hours = 1 minutes; Length of the car Y is ignored as compared to length of the bridge.
Since Car X takes 1 second less than car Y to pass the bridge.
Car X takes 59 seconds to pass the bridge.
Since the time when car X starts entering bridge is still unknown
NOT SUFFICIENT

IMO E

ashwini2k6jha · Answer

time taken by x=?

statement 1:nothing given about time taken by Y
not sufficient
Statement2 Not sufficient answer 
time taken by Y=1/2X30=1/60X3600=60 SECOND
NOTHING given about x
1+2: sufficient Answer C
time taken by x=60-3+2=59

Raxit85 · Answer

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.
Let's try different cases.
Case 1:
Car Y starts at 6:00:10 and finishes at 6:00:15.
Total time = 5 seconds.
Car X starts at 6:00:13 (3 seconds after Car Y) and finishes at 6:00:17 (2 seconds after Car Y).
Total time = 4 seconds.

Case 2:
Car Y starts at 6:00:10 and finishes at 6:00:20.
Total time = 10 seconds.
Car X starts at 6:00:13 (3 seconds after Car Y) and finishes at 6:00:22 (2 seconds after Car Y).
Total time = 9 seconds.

The cases above illustrate that Car X's time is one second less than Car Y's time.
No way to determine Car X's exact time.
INSUFFICIENT.

2) Car Y traveled across the bridge at a constant speed of 30 miles per hour.
Car Y's time = d/r = (1/2)/(30) = 1/60 hour = 1 minute = 60 seconds.
No way to determine Car X's time.

1) + 2)
Since Car Y's time = 60 seconds, and Car X's time is 1 second less, Car X's time = 60-1 = 59 seconds.
SUFFICIENT.
Ans. C

adonouis · Answer

The correct answer is C.

let time needed to cross the bridge for car X be tx, and for car Y be ty.

1. Statement 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
It means car X needs 1 second less to travel across the bridge than car Y
thus, ty=tx+1

But, this is not enough to tell about tx or ty.

2. Statement 2: Car Y traveled across the bridge at a constant speed of 30 miles per hour.
i.e 1/2 mile per minute or 1/2 mile per second. Since the bridge is 1/2 mile long. So, car Y will take exactly 60 sec to cross the bridge.
thus, ty = 60

But, this alone is not enough to state about car X and time tx.

3. Considering both statement 1 and 2.
we have, 
equation (i) ty = tx + 1
equation (ii) ty = 60
Putting the value of ty in equation 1,
we get, 60= tx + 1
 tx= 60 - 1
 tx= 59.

Thus, both statement together are sufficient.

techwave · Answer

Ans: C Both statements together are sufficient.

Prompt:

Total Distance of bridge= 0.5 Mile

Time for X to cross the bridge(Tx)

1) Car Y

assume starting time is Ts and end Time is Te respectively when Car Y starts and ends the half mile journey on bridge.
Velocity = Vy
Distance traveled Sy= (Te-Ts) * Vy

Car X

Time taken = Te+3-(Ts-2) = Te-Ts +5 --- (1)

Lots of unknowns hence not sufficient

2) Vy=30 mph

S=VT on substituting.

This will give us Te-Ts. Not sufficient

Both statements combined.

we can substitute Te-Ts. Hence C.

Archit3110 · Answer

#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.
speed of x * ( t+3) = speed of y * t
and speed of x * ( t+2)= speed of y*t
since both are in same direction we can say that
speed of x*(t+1) = speed of y * t

value not know insufficient
#2
Car Y travelled across the bridge at a constant speed of 30 miles per hour
from this we can determine the time it takes for y to cross 1/2 mile bridge sufficient
30 mph in seconds = 30/3600 ; 1/120
time taken = 1/2 *120 ; 60 seconds
but we dont know any relation of x & y ; insufficient
from 1 &2
we can determine the time it would take x to cross
IMO C

If Car X followed Car Y across a certain bridge that is 1/2 mile long, what is the time when Car X pass 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 travelled across the bridge at a constant speed of 30 miles per hour

AnirudhaS · Answer

question stem says - bridge length is 1/2 miles
(1) X took 1 sec less than Y. Not sufficient.
(2) Y speed is 30 mph. Not sufficient.
(1)+(2) Car Y takes =  \frac{1}{2}*\frac{1}{30} = \frac{1}{60} hr  = 60 sec
Therefore, X takes = 59 sec (Sufficient)
Answer: C

bM22 · Answer

Answer C.
Solution:

(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.

let time taken by car X be x sec and time taken by car Y be y seconds. Now from the statement we can see that car X takes 1 sec less to cross the bridge as compared to car Y.

x=y - 1
But we still cannot calculate x.
So  Insufficient .

(2) Car Y traveled across the bridge at a constant speed of 30 miles per hour

since, Car Y can travel 30 miles ---- in 60 mins, => 1 mile in 2 mins => 1/2 mile in 60 secs.

But still nothing is know about car X so  insufficient .

But if both are put together: x = 60 - 1 = 59 seconds.  Sufficient . => C.

shameekv1989 · Answer

If Car X followed Car Y across a certain bridge that is 1/2 mile long, what is the time when Car X pass 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 travelled across the bridge at a constant speed of 30 miles per hour

Question is asking the time when Car X passes the bridge not the total time taken to pass the bridge.

No options give us the time in absolute terms. Hence Insufficient.

ANSWER - E

If it were asking total time taken for X to pass the bridge. 
i) Car X will take 1 sec less than time taken by Car Y to pass the bridge. 
ii) We can determine time taken by Car Y to pass the bridge.

Combining i) and ii) we can determine time taken by Car X.

MARVEL13 · Answer

Bridge Length ==> Distance = .5 mile
Time taken by x ==??

First Check S2 
Y Speed 30 Miles per Hour. Doesn’t give any information about x. So NOT INSUFICIENT

S1 
X took 1 second less than Y. But we don’t know that how much time Y took? So INSUFFICIENT

S1 & S2 together 
Together also it won't be sufficient. As we know Y drives 30 Miles per Hour. So, Y will drive ½ mile in 1 minute. As X took 1 second less, it will take 59 Seconds.

But we won't be able to know the The time when X passes the bridge.

ANSWER--> E

sonam.gupta · Answer

Correct Answer is C. Its wrong here.

GMATBusters · Answer

Have you read the question and explanation above?
 Learn to unlearn and unlearn to learn

vishumangal · Answer

Hi Sir,

I would like to say that the Question is poorly constructed in terms of the verbal usage.

who writes like this, what is the time when car passed the bridge.

At what time car passed the bridge is more correct and Clear.

Secondly, Just read the statement one. One is not able to figure who drove onto and drove off the bridge.

Correct way of saying statement one would of have been (1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and Car X drove off the bridge exactly 2 seconds after Car Y drove off the bridge.

GMAC used high standards in writing a question to make sure that meaning is cleared. Just by making the wording ambiguous does not make the question of high quality. If the statement 1 would have constructed nicely than it is sub-600 level question.

GMATBusters · Answer

Thanks for looking at my question and providing feedback, I really appreciate that.
Great to hear that you have a strong hold at SC which is the most dreaded section of the GMAT.

I am not an expert in SC however, the points are worth to be noted:
1) " who writes like this, what is the time when car passed the bridge.

At what time car passed the bridge is more correct and Clear." 
 you cannot eliminate any option or consider an answer option wrong if you know another popular way of saying the same thing.

2)  " (1) Car X drove onto the bridge exactly 3 seconds after Car Y drove onto the bridge and Car X drove off the bridge exactly 2 seconds after Car Y drove off the bridge." 
Statement 1 is taken verbatim from an official question only.
See the official question here :  https://gmatclub.com/forum/if-car-x-followed-car-y-across-a-certain-bridge-that-is-137221.html#p1112600 .

Happy Learning

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If Car X followed Car Y across a certain bridge that is 1/2 mile long,

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