2 cars are 120 miles apart.If both cars go at a constant speed with one of them going at 30/mph and the other 40/mph – how far apart will the 2 cars be in exactly 1 hour before they meet?
A) 10
B) 50
C) 70
D) 110
E) None of these
2 cars are 120 miles apart
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70
c)
1hour=120-(30+40)=50
2hours=120-(60+80)=-20(already met)
50
1hour=120-(30+40)=50
2hours=120-(60+80)=-20(already met)
50
Distance – 120
Combined Speed – 70
Time reqd 1 and 5/7 hours
SO 1 hr before they meet means only 5/7 hrs spent
i.e. 5/7*70 =50 only
So ans= 120-50 = 70
SO (C) is correct
Ans is D i.e. 70.
Time to meet = D/va+vb = 120/70=12/7
Time (one hour before)=12/7-1=5/7 hr
Distance travelled by 1st car= 30*5/7=150/7
Distance travelled by 2nd car= 40*5/7=200/7
Total distance travelled by both the cars = 150/7+200/7=350/7=50
Remaining distance (what we need to calculate) = 120-50=70
Sorry for D its C. The explanation remains same
Ans is E.
Since the direction of cars not given, we can’t find the correct answer.
The distance between 2 cars exactly 1 hour before they meet =>
Relative velocity
So,
when they are moving in opposite direction => 40+30=70
when they are moving in same direction (40mph car chasing 30mph car) => 40-30=10.
E
I Agree.
SInce the direction is not given it is not possible to find the exact distance.
The question contains “before they meet” which provides hint that they are moving in the same direction.
Ans – C
I agree with Murali.
As in 1 hr they travel 70 Kms, so exactly 1 hr b4 they meet their distace is 120-70 i.e. 50 km.
So, the answer is B
Sorry, its 70
Answer is C
50
50
Alright!
The question is indirectly asking us “the TOTAL distance traveled by the 2 cars”.
This is dependent on their relative speed.
If the cars are moving in opp. directions, rel. speed= 70
But, if cars are moving in same directions, rel. speed= 10
So, we cannot determine FOR SURE what total distance they would travel in 1 hr. as the direction is not specified (or implied)
AP, you are incorrect there since the 2 cars can still meet even when they are traveling in the same direction. The faster car would “catch up” with the smaller.
Let’s take another approach – the straightforward mathematical approach.
Let, r be the rel. speed.
and t be the time after which they meet.
Situation 1 – opp. direction.
r=70
70*t = 120 => t=12/7
1 hr before they meet => time = t-1
dist. traveled by A = 40*(t-1) and dist. traveled by B = 30*(t-1)
Total dist. = 40*(t-1) + 30*(t-1) = 70(t-1) = 70(12/7 – 1) = 50
Now,
Situation 2 – same direction.
r=10
10*t = 120 => t=12
1 hr before they meet => time = t-1
dist. traveled by A = 40*(t-1) and dist. traveled by B = 30*(t-1)
Total dist. = 40*(t-1) - 30*(t-1) = 10(t-1) = 10(12 – 1) = 110
Answers from Situation 2 and Situation 2 do not match.
So, this question cannot be solved, UNTIL we know the directions in which the cars are traveling.
HTH
~magnus1
And Kudos to Murali for that precise explanation.
~magnus1
C
Ans: 70
Traveling in the same direction:
>________B>____________120m________________A>______>>>
40mph 30mph
When they meet, the distances travelled will be –
Let Dist. travelled by B -> DB, Dist. travelled by A -> DA
DB = 120 + DA
40t = 120 + 30t
10t = 120.
t = 12. —> The time after which they will meet.
1 hr before = 11 hrs.
DA in 11 hrs = 30 * 11 = 330 m
DB in 11 hrs = 40 * 11 = 440 m
So, the dist they are apart = 110 m.
I am more or less confident, this calc is correct.
But am confused about this – If 1 hr before they meet, they are 110 m apart, How can they meet in 1 hr since the B is travelling only at 40 mph and surely cannot cover 110 m in 1 hr??? Am I asking stupid question here …??
My answer is A…
40mph 30mph
A— 120 miles —B
For every hour, the distance will keep on reducing by 10 miles. Hence, the answer to question: “how far apart will the 2 cars be in exactly 1 hour before they meet?” will be 10 miles.
Answer should be A…
Experts, please comment on this and provide official answer.
cheers…
the answer is C. As both car covers 70 km distance in one hour. ‘Take the gmat’ please confirm
Answer is A, 10 miles apart.
1. calculate the time that they will meet:
Let A be the slower, B the faster:
30Tmeet=Da
40Tmeet=Da+120
40Tmeet=30Tmeet+120
10Tmeet=120
Tmeet=12Hours
1 before =11
2. Now calculate the distne both have trav in 11 hrs
Da=330
Db=440
BUT A has a lead of 120 (or B a lag of 120) so either add 120 to A or subtract 120 from B–>B=320 so the diff is 10, answer is A
the answer wud be c
no doubts the answer is E .. and that is the reason y the choice has been given .
Since it is not mentioned in which direction cars are travelling, hence different ans will be there according to their directions. i.e. 30+40 Km if in opposite direction and (40-30)= 10 Km in same direction.
hence ans should be
E.
what is the OA?
GMAT Team should tell…
OA??
Correct answer is C ie 70.
E
A & C both are correct… if we assume direction ourselves…
but GMAT is abt to check this…
The correct answer is E
what this”Take GMAT Team” is answering is absurd…
Magnus n Murali … Cheers!!!!
My Simple question :::
Is it possible to meet two cars if the are going away from each other ?
2 cars are……………………….. be in exactly 1 hour before they meet?
take gmat team
you answered wrong, in the gmat that it’s an ambiguous question because no direction is given.
Answering your question: no, they can’t meet if they go away from each other in a straight line.
Now, they can go straight towards each other (which is your assumption) or the can go zig-zag or doing an arc or whatever other way you like towards each other. They might even go at angles. The gmat would not ask a question like that without providing that simple detail otherwise the answer is E… since there is no way to solve it.
hi dear Take GMAT team
if both of them travel in the same direction. that is if the 40 mph is chaisng the 30 mph guy then answer will be ten
however if both are on a collision path then it will be 70
if 30 mph is chasing the 40 mph then there is no way they are going to meet
still there are two way possible
please accept ur mistake with grace! it is humans who make mistakes
Agree with himanshu and joaquin. Take GMAT team, please provide the answer.
the ans is C,
50
Since the direction is not given ..
whether the cars r moving in same direction or opposite direction ?
so its like can’t say …
coz if they go in same direction then provided (40 mph car is chasing 30 mph car) .. its 10
if in opp. direction then , 70 …
b 50
simple logic
faster car follows in same direction as slower car
faster car 40mph be A
slower car ahead by 120m at speed 30mph be B
in 12 hrs they will meet at exactly 480m from starting point of A(FASTERCAR)
one hour before A will be in 440m and B will be in 450m
assume A starts from 0 miles and write o,40,80 and so on
B starts from 120m and write 120,150,180 so on
just check which hour they will be in same distance it would be in 12th hour!!!then see in 11 hours where they are!!THATS IT!!!
so answer is 10miles apart!!!
70
ans is non of these E
since they have not given the direction.
its b-50
this is really wierd question and dont see an answer to it. the best answer would be E.
If cars are going in same direction then
1. if the slower car is at 0 miles and faster at 120 miles, they will never meet.
2. if the faster car is at 0 miles and faster car is at 120 miles then the distance shoudl be calculated 0,40,80, 120, 160, 200, 240, 280, 320, 360, 400, 440, 480
and for slower car it goes like , 120, 150, 180, 210, 240, 270, 300, 330, 360, 390, 420, 450, 480.
the cars meet at 480 miles and an hr ago they were 10 miles far.
But if the cars are going in different directons then they never met.
so basically the cars are not meeting in to scenarios. the answer should be E.
The ans can be 10 or 70
If the two cars are moving in the same direction and the slower one (30mph) is being followed by the faster one the ans is 10
Whereas if they are moving towards each other the ans is 70
To be on the safer side I would mark 70 as my ans
Ans is 70, which is C
Let say Car A travels @ 30 mph and car B @ 40 mph
1 hour before they meet, both the cars travel for 5/7 hours of time
So in 5/7 hours, A travelled 150/7 miles and B travelled 200/7 miles
Togathr they travelled 50 miles(i.e. distance they both covered 1 hour before they meet)
Total distance to be covered 120 miles
Distance they covered = 50 miles
Distance left = 70 miles
Ans is 70, which is C
How I calculated 5/7 hours …..
Ans : Car A travels @ 30 mph and car B @ 40
Total distance to be covered : 120
Time they will take to cover : 120/70 ( 70 = 30+40)
In 12/7 hours, they will meet. But question asks us, what distance they would have covered 1 hour before they meet
so 12/7 minus 1 = 12/7 – 1 = 5/7
Then just find how much car A travelled in 5/7 hours and how much Car B travelld in 5/7 hours, add the distance and minues it from the Total distance to be covered.
Regards
A.c.
c
As explanation given by sachin below Ans is b i.e. 50.
Time to meet = D/va+vb = 120/70=12/7
Time (one hour before)=12/7-1=5/7 hr
Distance travelled by 1st car= 30*5/7=150/7
Distance travelled by 2nd car= 40*5/7=200/7
Total distance travelled by both the cars = 150/7+200/7=350/7=50
No need to substract 50 from 120 as it is not required…
The answer is 10 miles.
The answer is 70
ie 70 miles as the relative speed is 70 mph(30+40)
The question boils down to how much distance both will travel in 1 hour
I realize I’m late but there are two scenarios where the two cars will
MEET.
1) They could be going towards each other.
2) They could be going in the same direction and meet provided the car in the rear is going faster then the car in front. They will eventually meet even if the car in the rear is going only 1 mph faster than the car in front.
The question doesn’t state any of these directions it cannot be answered except for choice E.
Answer is C
distance travelled by two cars in one hour is 30 *1 + 40* 1 =70
hence he is asking about ” how far apart will the 2 cars be in exactly 1 hour before they meet ” hence they will be 120 – 70 = 50
If both the cars are moving in opposite direction, then
speed =30 + 40 =70km/hr
Distance = 120km
Time = 1 5/7
Distance, 1hr Before they meet =5/7*70 = 50kms, is the distance travelled by cars, distance left = 120 – 50 = 70
If both of them moving in same direction??? but care moving with 40km/hr should chase care moving with 3o km/hr , then inly they can meet at some point of time.
So average soeed would be 10 km/hr,
time = 12 hrs,
Before 1 hr they meet i.e distance traelled in 11 kms
= 10 *11= 110 km
I think the question needs more clearity….
Ans E
1: In same direction ans is D 110
2: In opposite direction ans is C 70
But since in question no where the direction is given so the ans is E it can be D or C.
So ans is E
E since no direction is given both 70 and 110 are possible if direction is mentioned.
Question : – 2 cars are 120 miles apart.If both cars go at a constant speed with one of them going at 30/mph and the other 40/mph – how far apart will the 2 cars be in exactly 1 hour before they meet?
Solution : – This is so simple and straight forward question..
u guys don’t even need any calculations..
it is clear that cars will meet after 12 hours. i.e.
Let car A travelling at 30/mph will cover 360* miles, and it is already 120 miles ahead of car B, tarvelling at 40/mph.
Car B will cover 480* miles to meet car A after 12 hours.
*Speed x Time = Distance
At the time of 11th hour car A will cover 450(330+120) miles and car B will cover 440 miles.
They will meet at distace of 480 miles.
So, 2 cars will be 10 miles far from each other exactly 1 hour before they meet.
Hence Answer is — “A”
Thanks & Regards
***** and if cars are moving in the opposite direction & in a atraight line, then its impossible that they will meet at any point.
Cheers…..!!!
The question is totaly wotthless as it is not telling us about respective directions of the cars….!!!
But u all guys are wrong if we talk, when cars are moving in the same direction
Daveparthiv
Robin
Alok Singh
Harmeet
Adarash
jasneet Juneja
Murali
You guys are right for the option when cars are moving in the same direction.
Let d= 120 miles (two cars are apart)
two cars starts traveling at same time say x hr.
30x+40x=120(since both starts journey at same time and meet at x hr. with their respective speed)
hence, x=12/7 hr we get.this is the time when two cars meet each other.
now, 1 hr before so, x”=(12/7-1)hr. x”=5/7 hr. at this time cars are how much apart we need to find. The total distance travelled by both cars in x” hrs are 30×5/7 + 40×5/7=50 miles total traveled and though remains 1 hr apart.
now.The distance remains to travel is 120-50= 70 miles.
C answer is 70