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:
250 comments Page 13 of 25.
Dileep kumar said:
1 decade ago
Distance = speed/time;
Let us bridge length = x say, train travelling distance = 130 m.
The total distance is = x+130;
Speed = 25/2;time = 30sec;
:: x+130 = (25/2) 30;
x = 375-130;
= 245.
Let us bridge length = x say, train travelling distance = 130 m.
The total distance is = x+130;
Speed = 25/2;time = 30sec;
:: x+130 = (25/2) 30;
x = 375-130;
= 245.
Sunil Kumar said:
1 decade ago
Let bridge length x m then.
Length of train = 130.
Speed 45*5/18 = 12.5.
Distance=12.5*30 = 375.0-130 = 245.
Length of train = 130.
Speed 45*5/18 = 12.5.
Distance=12.5*30 = 375.0-130 = 245.
Sanjay said:
1 decade ago
B.L. = Bridge Length.
For crossing the bridge distance should be 130+ (B.L) +130.
Then why you are taking 130 + B.L?
For crossing the bridge distance should be 130+ (B.L) +130.
Then why you are taking 130 + B.L?
Thamilarasan said:
1 decade ago
Have any common formulas for easily learning?
Dumpati Mahesh said:
1 decade ago
Here we should consider as per the problem that, Train is passing only one time through the bridge. So 130+B.L. Only sanjay.
P.Deepika said:
1 decade ago
I Had one doubt.,
Crossing means we want to consider as opposite direction as formula (u-v) as (375-130) = 245?
Is This Write Or Wrong, If Any One Please Answer Me.
Crossing means we want to consider as opposite direction as formula (u-v) as (375-130) = 245?
Is This Write Or Wrong, If Any One Please Answer Me.
Dileep kumar said:
1 decade ago
Hai friends don't be confuse with considering different formulas, let use single formula to solve these all type of questions, i.e.
Distance = speed*time; OR (D = ST) ;
Let us consider bridge length = x;
Total length (x+130) = (25/2) *30;
x + 130 = 375;
x = 375-130;
x = 245.
Distance = speed*time; OR (D = ST) ;
Let us consider bridge length = x;
Total length (x+130) = (25/2) *30;
x + 130 = 375;
x = 375-130;
x = 245.
Lovepreet kaur said:
1 decade ago
I have solved this problem in another way.
Here am explaining it.
Distance=speed*time;
Length of train = 130m.
Speed = 45 km/hr or 45*1000/3600 m/sec.
Time = 30 sec.
Length = (45*1000/3600)*30 = 375m.
Length of bridge = 375-130 = 245m.
Here am explaining it.
Distance=speed*time;
Length of train = 130m.
Speed = 45 km/hr or 45*1000/3600 m/sec.
Time = 30 sec.
Length = (45*1000/3600)*30 = 375m.
Length of bridge = 375-130 = 245m.
Rajesh said:
1 decade ago
Hi friends, for most of these questions, just understanding the questions is enough and you don't need any formulas.
In the above problem train passes at 45 km/hr so for 1s it will go (45*5/18) = 12.5 m.
And for 30 s it will go 12. 5 * 30 = 375 m.
But we have to reduce trains length (for crossing a pole or person or bridge). So 375-130 = 245 m.
In the above problem train passes at 45 km/hr so for 1s it will go (45*5/18) = 12.5 m.
And for 30 s it will go 12. 5 * 30 = 375 m.
But we have to reduce trains length (for crossing a pole or person or bridge). So 375-130 = 245 m.
Riyaz said:
1 decade ago
Hi !
Actually we don't know the length of the bridge so we have to assume 'x' as like length of the bridge.
The answer is in meters so we should have to convert 45 km/hr in meters. Because it is in km/hr that's why we are using 5/18.45*5/18 = 25/2.
Train travelling distance and time is 130m+x/30sec = 25/2.
After that we need to find 'x' that is 2 (130+x) = 750. If you solve this equation then you can get 'x' that's the answer.
Actually we don't know the length of the bridge so we have to assume 'x' as like length of the bridge.
The answer is in meters so we should have to convert 45 km/hr in meters. Because it is in km/hr that's why we are using 5/18.45*5/18 = 25/2.
Train travelling distance and time is 130m+x/30sec = 25/2.
After that we need to find 'x' that is 2 (130+x) = 750. If you solve this equation then you can get 'x' that's the answer.
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