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E
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Difficulty:
45%
(medium)
Question Stats:
68% (01:46) correct
32%
(02:03)
wrong
based on 660
sessions
History
Date
Time
Result
Not Attempted Yet
If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?
(A) 10
(B) 30
(C) 40
(D) 50
(E) 70
(A) 10
(B) 30
(C) 40
(D) 50
(E) 70
As the question ask how far apart they will be 1 hour before they meet, I first calculated when they meet : 120- (30+40)= 12/7 h
so one hour before they meet is 12/7 - 1 = 5/7 h.
when the time is 5/7 they are 5/7 *70= 50 miles far apart .
anyway, the Question bank says that the correct answer is E, 70.
Can anyone tell me why? I think 70 is how much they are far apart 1 hour after they leave, not 1 hour before they meet.
so one hour before they meet is 12/7 - 1 = 5/7 h.
when the time is 5/7 they are 5/7 *70= 50 miles far apart .
anyway, the Question bank says that the correct answer is E, 70.
Can anyone tell me why? I think 70 is how much they are far apart 1 hour after they leave, not 1 hour before they meet.
01 Oct 2016, 03:23
Kudos
Bookmarks
mc563427
The combined rate of the two trains is 30 + 40 = 70 miles per hour. Therefore 1 hour before they meet the must be 70 miles apart (in the final 1 hour they will cover 70 miles to meet).
Answer: E.
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17 Oct 2016, 06:30
Kudos
Bookmarks
this is a little lengthier way of doing but mistake proof method.
They would meet in 120/70 = 12/7 hours
1 hour earlier 5/7 hours
distance between trains = total distance -(distance covered by train A + distance covered by train B)
= 120-(5/7(40+30)) [ distance of A = 5/7* 40; like wise distance by B]
= 70 Km
Kudos! if u like this
They would meet in 120/70 = 12/7 hours
1 hour earlier 5/7 hours
distance between trains = total distance -(distance covered by train A + distance covered by train B)
= 120-(5/7(40+30)) [ distance of A = 5/7* 40; like wise distance by B]
= 70 Km
Kudos! if u like this
