Aptitude - Problems on Trains - Discussion
Discussion Forum : Problems on Trains - General Questions (Q.No. 3)
3.
The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:
Answer: Option
Explanation:
| Speed = |  |
45 x | 5 |  m/sec |
= | |
25 | m/sec. |
| 18 | 2 |
Time = 30 sec.
Let the length of bridge be x metres.
| Then, | 130 + x | = | 25 |
| 30 | 2 |
2(130 + x) = 750
x = 245 m.
Video Explanation: https://youtu.be/M_d8WufJWKc
Discussion:
247 comments Page 11 of 25.
SK Lodhi said:
1 decade ago
130+B = 30 Sec.*45*5/18 m/s(time*speed).
130+B = 375 m.
Where B = length of the Bridge = 375 - 130 = 245 meters.
130+B = 375 m.
Where B = length of the Bridge = 375 - 130 = 245 meters.
Radha said:
1 decade ago
Please explain method clearly how we will dot 750?
Safina M said:
1 decade ago
Hey Radha,
Cross multiply (139+x)/30=25/2 i.e,
2*(130+x)=30*25.
i.e., 260+2x=750.
2x=750-260.
2x=490.
x=490/2.
Hence, x=245.
Cross multiply (139+x)/30=25/2 i.e,
2*(130+x)=30*25.
i.e., 260+2x=750.
2x=750-260.
2x=490.
x=490/2.
Hence, x=245.
Jagabandhu patra said:
1 decade ago
(45000/3600*30)-130 = 245.
(1)
Varalakshmi saravanan said:
1 decade ago
Hi Friends it's very simple.
Length of the Train = 130 m.
Speed = 45 km/hr after converting into m/s we will get (45*5/18) => 25/2.
Time = 30 sec.
Length of bridge = x + length of train.
X+length of train = Speed of the train*time.
X+130 = 25/2*30.
X+130 = 375.
X = 375-130.
X = 245.
Length of the Train = 130 m.
Speed = 45 km/hr after converting into m/s we will get (45*5/18) => 25/2.
Time = 30 sec.
Length of bridge = x + length of train.
X+length of train = Speed of the train*time.
X+130 = 25/2*30.
X+130 = 375.
X = 375-130.
X = 245.
Vishali said:
1 decade ago
Hi friends I did in a different way:
Let the length of train b = 130.
Let the length of bridge b = x.
Therefore distance = x+130.
Time = 30 sec.
S = 45 km/h = 45*5/18 = 25/2 m/s.
So, in this case distance = 375 m.
So, d = x+130 substituting the value of d (distance).
We get 375-130 = x.
x = 245m.
Let the length of train b = 130.
Let the length of bridge b = x.
Therefore distance = x+130.
Time = 30 sec.
S = 45 km/h = 45*5/18 = 25/2 m/s.
So, in this case distance = 375 m.
So, d = x+130 substituting the value of d (distance).
We get 375-130 = x.
x = 245m.
(1)
Sohail Khan said:
1 decade ago
We know that:
Time = Distance/Speed.
Suppose length of the bridge is X mtr.
Length of the train is 130 mtr.
So total distance = 130+X.
30 = (130+X)/45*(5/18).
Then the value of X is 245 mtr.
Time = Distance/Speed.
Suppose length of the bridge is X mtr.
Length of the train is 130 mtr.
So total distance = 130+X.
30 = (130+X)/45*(5/18).
Then the value of X is 245 mtr.
(1)
Ramkumar gadi said:
1 decade ago
Time taken by the train to cross object which is in motion in relative motion we have formulas:
T = (a+b)/(U+V) and T = (a+b)/(U-V).
Let be b = x.
So here we have U = Speed of train; a = Length of train = 130m.
V = Speed of object; B = Length of object.
V = 0; b = x; T = 30s.
S = 45 km/h = 45*5/18 = 25/2 m/s.
30 = (130+x)/(25/2+0).
= 30+25/2 = 130+x.
x = 245m.
T = (a+b)/(U+V) and T = (a+b)/(U-V).
Let be b = x.
So here we have U = Speed of train; a = Length of train = 130m.
V = Speed of object; B = Length of object.
V = 0; b = x; T = 30s.
S = 45 km/h = 45*5/18 = 25/2 m/s.
30 = (130+x)/(25/2+0).
= 30+25/2 = 130+x.
x = 245m.
(1)
Sivakumar.s said:
1 decade ago
Train 130 meters long. Travel 45 km/hr.
To convert m/s = 25/2.
So 2 second train will move 25 meter. So 30 second means.
2*15 = 30 second.
25*15 = 375.
So train travelling 375 meters to reduce the train meters.
375-130 = 245.
So the bridge meter is 245 meters.
To convert m/s = 25/2.
So 2 second train will move 25 meter. So 30 second means.
2*15 = 30 second.
25*15 = 375.
So train travelling 375 meters to reduce the train meters.
375-130 = 245.
So the bridge meter is 245 meters.
(1)
Deep said:
1 decade ago
Easy method is by using time and distance formula.
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