GRE Math Question

prolific
#1. October 11th, 2008, at 9:11 PM.

e. 70 miles

if they’re one hour away, each train will move how many miles they can move in one hour according to their speed. Train 1 will have to move 30 miles, and train 2, 40. Therefore, 30+40 = 70 miles away from each other.

Pruthvey
#2. October 11th, 2008, at 9:11 PM.

e-70 miles

Relative speed=70mph
Time taken to collide=120/70 hr

1hr before would be 5/7th of an hour..

In 5/7th of an hour 1st train covers 5/7(30) miles and second train does 5/7(40) miles..

The distance b/w them would be 120 -5/7(30 +40)=70

Kofi
#3. October 11th, 2008, at 10:13 PM.

70

uday
#4. October 11th, 2008, at 11:04 PM.

EEEEEEEEEEEEEEEEE>>>>>>>>>>>>70 miles

Alexandra
#5. October 11th, 2008, at 11:24 PM.

D. 50
Would it be 50 miles? The trains both travel 70 miles during the hour but then the remaining distance between them would be (120-70) = 50 miles.

payam
#6. October 12th, 2008, at 12:08 AM.

70 miles

30+40=70

Aditya
#7. October 12th, 2008, at 12:47 AM.

it would be fifty coz the trains will cover a total distance of 70 and the remaining distance between them is 120-70=50.

Shubham Shukl
#8. October 12th, 2008, at 1:22 AM.

I think it should be 50…

pregas
#9. October 12th, 2008, at 5:48 AM.

70 would be total distance covered and the distance would be the diff b/w 120 and 70 which is 50 miles

pari
#10. October 12th, 2008, at 9:25 AM.

its 50. in 1hr train 1 will cover 40 miles and train 2 will cover 30 miles. so totally 70 miles in 1hr is traveled. so remaining is 120-70=50 miles

kaushik
#11. October 12th, 2008, at 12:18 PM.

its 50.

Gaurav
#12. October 12th, 2008, at 1:50 PM.

70 miles more would the trins have to travel before they meet each other, because its 1 hour more they have to travel.

ANS…70 miles

pari
#13. October 12th, 2008, at 5:49 PM.

sorry frnds, it cant be 50… it is 70 only
in 1hr 70 miles is covered. so to cover 120 miles time taken is 1.7 hrs.. ( so in 0.7 hrs remaining 50 miles is covered)
1.7 hr = 1hr + 0.7 hr
or
1.7 hr= 0.7 hr+ 1 hr
which means, 120 miles = 50 miles+ 70 miles
so 50 miles is covered in 0.7 hrs and remaining distance 70 miles is distance to be covered in 1 hr (ie) before 1 hr they are 70 miles away…

siddharth
#14. October 13th, 2008, at 8:50 PM.

the answer is 70 miles…..
the trains will meey at
x/30=(120-x)/40
x=360/7 from first station
thus they meet after
360/7/30=12/7 hrs
one hour before
means 12/7-1=5/7 hrs
means 1st train travels 150/7 nd snd trn 200/7

tot dist =350/7= 50 miles

thus dist betn them =120-50=70 miles

william
#15. October 14th, 2008, at 9:54 PM.

E. 70 miles.
The starting distance is unimportant. The distant the trains will be apart 1 hour before meeting is the key. Start at the train meeting and move time back 1 hour. The trains start at 0 miles apart. In 1 hour: Train A travels 40 miles, Train B travel 30 miles = 70 miles apart.
The answer of 50 was given, but can easily be ruled out by rewording the question. If two trains are 50 miles apart and traveling towards each other, Train A at 40mph and Train B at 30 mph how long will it take for them to meet? You guessed it right, it’s not one hour.

Chloe Keveryn
#16. October 15th, 2008, at 9:11 PM.

E.

gurudutt
#17. October 17th, 2008, at 4:45 PM.

distance covered by both trains in 1hour is 70 and total dist. is 120 so remaining d .t is 120-70=50

Soberboy
#18. November 2nd, 2008, at 9:32 PM.

The answer is 50 and here is why

We wanna find time, let time = x
30x + 40x = 120
70x = 120
x = 12/7 hour

12/7 hour is the time needed for both of the trains to meet each other.

The question required the distance before 1 hour.
12/7 hour - 1 hour = 5/7 hour

So, the distance is 30(5/7hr) + 40 (5/7hr) = 70 (5/7hr) = 50 miles ..bingo!