Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 11)
11.
A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the length of the other train?
Answer: Option
Explanation:
Relative speed = (120 + 80) km/hr
| = |  |
200 x | 5 |  m/sec |
| 18 |
| = | |
500 | m/sec. |
| 9 |
Let the length of the other train be x metres.
| Then, | x + 270 | = | 500 |
| 9 | 9 |
x + 270 = 500
x = 230.
Discussion:
67 comments Page 2 of 7.
Priya said:
1 decade ago
Opposite direction: Adding.
Same Direction: Subtract.
Same Direction: Subtract.
(1)
Nikita said:
10 years ago
Right. But in the question trains are running in opposite side.
So speed is subtracted ie 120-80 = 40.
Am I correct?
So speed is subtracted ie 120-80 = 40.
Am I correct?
(1)
Srujana said:
9 years ago
Why we writing denominator 9 for x+270?
(1)
Onkar Babar said:
6 years ago
how we take x+270÷9? Please explain.
(1)
Alan said:
2 months ago
Here given two trains moving in opposite directions;
Formula:
Time = (L₁ + L₂) / (S₁ + S₂)
Given:
L₁ = 270 m
L₂ = ?
S₁ = 120 × 5/18 = 100/3 m/s.
S₂ = 80 × 5/18 = 200/9 m/s.
Substitute:
9 = (270 + L₂) / (100/3 + 200/9)
9 = (270 + L₂) / (500/9),
270 + L₂ = 9 × (500/9),
270 + L₂ = 500,
L₂ = 500 − 270,
L₂ = 230 m.
Formula:
Time = (L₁ + L₂) / (S₁ + S₂)
Given:
L₁ = 270 m
L₂ = ?
S₁ = 120 × 5/18 = 100/3 m/s.
S₂ = 80 × 5/18 = 200/9 m/s.
Substitute:
9 = (270 + L₂) / (100/3 + 200/9)
9 = (270 + L₂) / (500/9),
270 + L₂ = 9 × (500/9),
270 + L₂ = 500,
L₂ = 500 − 270,
L₂ = 230 m.
(1)
Rishikesh said:
1 year ago
Thanks everyone, for explaining it.
Bablu said:
8 years ago
What will happen if both trains are in the same direction as we relative velocity we can subtract but how the equation will come?
Please tell me.
Please tell me.
Anurag said:
1 decade ago
D = S*T = 270+x = 500/9*9.
So x = 500-270 = 230.
So x = 500-270 = 230.
Swathi said:
1 decade ago
Thanks alot. It is very helpful to me.
Arun said:
1 decade ago
When we add the relative speed when substract please tell me?
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