Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 13)
13.
Two trains, each 100 m long, moving in opposite directions, cross each other in 8 seconds. If one is moving twice as fast the other, then the speed of the faster train is:
Answer: Option
Explanation:
Let the speed of the slower train be x m/sec.
Then, speed of the faster train = 2x m/sec.
Relative speed = (x + 2x) m/sec = 3x m/sec.
 |
(100 + 100) | = 3x |
| 8 |
24x = 200
| x = |
25 | . |
| 3 |
| So, speed of the faster train = | 50 | m/sec |
| 3 |
| = |  |
50 | x | 18 |  km/hr |
| 3 | 5 |
= 60 km/hr.
Discussion:
75 comments Page 4 of 8.
Nutan said:
8 years ago
(50/3) * (18/3) = 60 how?
Shiva said:
1 decade ago
Why you are all talking always 5/18 to convert kmph into m/sec, I can't understand that logic, please explain reason behind that. Thanks in advance.
Sowdi said:
8 years ago
Thanks for your explanation @Sarang.
Punam said:
8 years ago
How come 50/3?
Manivel said:
7 years ago
@Punam.
Substitute the X value in faster train 2X, 2* (25/3) =50/3. M.
Substitute the X value in faster train 2X, 2* (25/3) =50/3. M.
Arifur Rahman said:
7 years ago
Let,
The speed of slower train be x m/sec.
The speed of faster train be 2x m/s.
Now,
(x+2x)÷2(two trains) = 100/8.
or,x=25/3.
The Speed of faster train = 2x = 2 * 25/3 = 50/3 m/sec * 18/5 = 60km/hr.
The speed of slower train be x m/sec.
The speed of faster train be 2x m/s.
Now,
(x+2x)÷2(two trains) = 100/8.
or,x=25/3.
The Speed of faster train = 2x = 2 * 25/3 = 50/3 m/sec * 18/5 = 60km/hr.
Dewansh said:
7 years ago
Why the relative speed is the sum of individual speeds rather than the difference?
Riqual said:
6 years ago
@Nutan.
How come 18/3?
How come 18/3?
Alan said:
2 months ago
Pattern: Two trains moving in opposite directions.
Formula: Time = (L₁ + L₂) / (S₁ + S₂).
Given:
L₁ = 100 m.
L₂ = 100 m.
Time = 8 s.
Let the slower train speed = S.
Then faster train speed = 2S.
Substitute:
8 = (100 + 100) / (S + 2S)
8 = 200 / 3S
24S = 200
S = 25/3 m/s
Faster Speed = 2S.
= 50/3 m/s.
Convert to km/hr:
50/3 × 18/5 = 60 km/hr.
Formula: Time = (L₁ + L₂) / (S₁ + S₂).
Given:
L₁ = 100 m.
L₂ = 100 m.
Time = 8 s.
Let the slower train speed = S.
Then faster train speed = 2S.
Substitute:
8 = (100 + 100) / (S + 2S)
8 = 200 / 3S
24S = 200
S = 25/3 m/s
Faster Speed = 2S.
= 50/3 m/s.
Convert to km/hr:
50/3 × 18/5 = 60 km/hr.
IKram said:
2 decades ago
Hey Jelli...
1) if 2 things moves in same direction:
time they meet t=(x+y)/(u-v)
where x,y-distance of trains or smthng
u,v-speed's in mps.
2) if 2 things moves in opposite direction:
time they meet t=(x+y)/(u+v)
1) if 2 things moves in same direction:
time they meet t=(x+y)/(u-v)
where x,y-distance of trains or smthng
u,v-speed's in mps.
2) if 2 things moves in opposite direction:
time they meet t=(x+y)/(u+v)
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