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# Aptitude - Problems on Trains - Discussion

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"If you judge people, you have no time to love them."
- Mother Teresa
3.

The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:

 [A]. 200 m [B]. 225 m [C]. 245 m [D]. 250 m

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.

 Uvitha said: (Sun, Jun 20, 2010 07:28:42 AM) Can you explain me in detail ?

 Nusrat Fathima said: (Sun, Jun 20, 2010 08:56:22 AM) I have solved this problem in a different way, is this right way to solve? speed=25/2 m/sec length of the bridge be x m total distance = speed * time x + 130 = 30 * 25/2 x + 130 = 375 x = 245 m is the above method to solve this problem right? Please help.

 Nusrat Fathima said: (Sun, Jun 20, 2010 09:07:45 AM) Hi Uvitha, Speed=25/2 m/sec then we find the lenght of the bridge using the formula distance/time = speed where distance = length of train + x Time = 30 sec & speed = 25/2 ``` 130 + x 25 ------- = -- 30 2``` => 245 m

 Sai said: (Sun, Jun 20, 2010 10:12:01 AM) Hi all, i've solved this problem in anotha way given, time=30 sec and speed=45km i.e 45x5/18 so im finding the distance= time x speed = 30 x 225/18 = 375m thus,the distance travelled by the train is 375m and the length given was 130m so 375-130 = 245m Now my question is..could someone insist me that the method followed by me is the right one?

 Karthik said: (Tue, Jun 22, 2010 06:49:56 AM) Yes fathima you are write.

 Nusrat Fathima said: (Fri, Jun 25, 2010 07:14:36 AM) Thanks karthik Sai the method mentioned by u is also a right method to solve the above problem..... Good thinking.

 Jose said: (Sat, Jul 24, 2010 06:11:11 PM) Hey how is possible to come ? 2(130 + x) = 750 x = 245 m. please advice me

 Naveen Kumar said: (Mon, Jul 26, 2010 05:42:55 AM) Hi jose, by cross mulyiplication method it will come as 2(130 + x) = 25*30 then 2(130 + x) = 750 then (130+x)=750/2 then (130+x)=375 then x=375-130 then finally ength of the bridge is 245m.

 Nattu said: (Tue, Jul 27, 2010 10:33:54 AM) But crossing chould mean the whole train should be off the bridge right? So why should we subtract the length of the train?

 Rahul said: (Wed, Jul 28, 2010 04:02:25 PM) @deepika @nattu speed= train length + bridge length ---------------------------- time taken to cross we know train length, speed and time taken. find out bridge length.

 Hari said: (Thu, Aug 12, 2010 12:53:21 AM) Super.

 Atul said: (Wed, Aug 25, 2010 04:29:32 AM) Plz give me trick to solve to this. Bcz compny gives 1 minute /question and question is so lengthy, then how can I mange my time.

 Mahes said: (Sat, Sep 18, 2010 08:06:15 AM) I have solved this problem in a different way, is this right way to solve? Speed = 25/2 m/sec Length of the bridge be x m. Total distance = Speed * Time x + 130 = 30 * 25/2 x + 130 = 375 x = 245 m Is the above method to solve this problem right? Please explain.

 Boopathi said: (Mon, Sep 27, 2010 05:40:10 AM) Hey how is it possible to come. 2 (130 + x) = 750. X = 245 m. Please advice me.

 Coolburn said: (Fri, Oct 15, 2010 09:57:00 PM) Hi, I had my own solustion on that 45 km/hr 1km = 1000m 1hr = 3600 sec 45 km/hr convert to metter =45000 m =3600 sec. 45000/3600 =12.5 Since 30 sec can cross the bridge =12.5*30 =375-130 =245m

 Gkvinodh said: (Fri, Oct 22, 2010 04:16:30 AM) How the equation (130 + x) /2 = 25/2 comes ?

 Mubeen said: (Wed, Nov 3, 2010 02:25:10 AM) @Coolburn Yep... Quite simple and understandable.

 Sunny said: (Sun, Nov 7, 2010 05:00:05 AM) Hey boopathi its simple. 2(130+x)=750 130+x=750/2 130+x=375 x=375-130 Therefore x = 245.

 Ruby said: (Fri, Nov 12, 2010 07:25:29 AM) Hey frnd........i sol dis prob in diff way.. length of train=130m speed=45km/hr time=30sec l=s*t l=(45*5/18)*30 l=(25/2)*30 l=375 length of bridge=l-length of train x=375-130 x=245m........... is dis is rite method????????

 Vijay Kumar Kuppani said: (Sun, Nov 21, 2010 09:06:02 AM) THE SIMPLEST WAY OF SOLVING THIS PROBLEM train speed=45km/hr=>45*(5/18)=25/2 m/sec; 25/2 m/sec means the train can travel a distance of 25/2 meters in 1 sec 1 sec--->25/2mts 30sec--->(25/2)*30=>375meters therefore the total distance covered by the train in 30 seconds is 375 meters(i,e train length+bridge length) by subtracting the train length from the total distance we can find out the length of the bridge i,e 375-130=245 meters

 Kalimuthu said: (Wed, Nov 24, 2010 01:39:10 AM) A train cross 1 hour =45km so that Trian cross in 1 hour =45000m(1km=1000m) so that trian cross in3600seconds=45000m(1hour=3600sec) so that trian cross in one second is 45000/3600=12.5m now 30 sec cross the bridge 12.5*30=375 so that trian length is 130m so we proof 375-130=245METERS

 Prakash said: (Tue, Dec 14, 2010 09:07:33 AM) speed=[45*(5/18)]=25/2 m/hr time=30 sec s=d/t distance= speed*time (25/2)* 30=375 375-130= 245 is this ryt

 Nirmala said: (Sat, Dec 18, 2010 03:32:39 AM) Why train length added with bridge length what's the logic behind it? Why bridge length is not subtracted from train length? Please clear my doubt.

 Sundaram said: (Thu, Dec 30, 2010 01:10:21 PM) Because train cross the bridge so we must add the length then only we will get the bridge length.

 A.Srinivas said: (Sat, Jan 1, 2011 11:42:19 AM) (x+130)/30=(45*5)/18

 Mannu said: (Sun, Jan 2, 2011 11:42:29 AM) What is the significance of train's length. Since the train crossed the bridge so distance should be of the bridge only. Why that bridge and train added?

 Janani said: (Sun, Jan 9, 2011 09:11:22 AM) How 5/18 came?plz xplain this..

 Murali said: (Wed, Jan 12, 2011 05:11:42 AM) @Mannu. Here we know only length of the train. We have to find the length of the bridge. We know the formula"s=d/t". Here distance is "L1+L2". Therefore "s= (L1+L2) /t". Now we will get the answer. By adding two distance only we will find the one distance (if you know the one distance then find the length of the train).

 Murali said: (Wed, Jan 12, 2011 05:23:34 AM) Hai! Janani while converting the distance it will come how means. I) if you convert km/hr into m/sec then multiplies with "5/18". Ii) if you convert m/sec into km/hr then multiplies with "18/5". In this way, above problem the train speed is convert into the km/hr into m/sec. (because the answer is given in the form of meters). Like this 5/18 will come.

 Periyasamy V said: (Fri, Jan 14, 2011 04:38:09 AM) I solved my own speed of the train 45km/hr,then change into 45000m/hr,then chang into per second (45000/3600)=12.5 m/sec,then multiple with 30sec,(12.5*30)=375, then mins the train length 375-130=245 i think this s correct......

 Raees said: (Wed, Jan 19, 2011 05:36:14 AM) Nusrath fathima solved method is better.

 Chithu said: (Wed, Jan 19, 2011 06:17:40 AM) Very useful methods.

 Rajan said: (Mon, Jan 31, 2011 08:08:37 AM) Periyasamy is perfectly correct and is the correct logic to solve the problem.

 Rohit said: (Thu, Feb 3, 2011 09:26:57 AM) < (end-point) train (start-point) >EntreR-----[BRIDGE]---< (end point) trian (start-point) >. When train end point meets bridge end point, according to this time is given 30 sec. So we have to add bridge length + train's length as total distance travelled in 30 sec. Two different way are given to solve this prblm.

 Rohit said: (Thu, Feb 3, 2011 10:27:51 AM) For just above explanation, bridge end point means, departure point of bridge.

 Nathy said: (Mon, Feb 14, 2011 01:05:01 PM) Sai's method of solving this problem is too simple and easy to understand. Thanks.

 Mannsoorkhan said: (Tue, Mar 15, 2011 01:38:03 AM) sai your explanation is clear and better explanation thanks to all

 Lokesh said: (Wed, Mar 23, 2011 08:47:36 AM) Actually bridge is a stationary object rite. So speed should be zero. Can u pls explain

 Mukesh said: (Thu, May 5, 2011 07:48:00 PM) Given..... train = 130m speed = 45 km/hr or (75/6)m/s time to cross bridge=30sec Bcos the time is in sec thtat why we convert time in m/sec by multiplying and dividing 45 by 1000 and 3600 respectively simple formula is distance=speed x time =(75/6) x 30 =375 meters now this distance is the distance which include train length also so less train length from this =375-130 =245 meters hence we get the ans

 Rajeev R T said: (Thu, May 12, 2011 03:14:30 AM) If the train is travelling 45 km per hr, then in one min.it can travel 750m, and in 1 sec it can travel 12.5m. then in 30 sec it can travel 375.00 m. As in 375m the length of the train is included, deduct the length of the train from the 375.00m, i.e 245.00m.

 Sarvjeet said: (Thu, May 26, 2011 11:30:45 AM) Length of the train= 130. Speed of the train = 45km/hr. time=30sec. lengthof bridge = x+length of train. x+length of train = Speed of the train *time. x+130=45*5/18*30. x+130 =375 x=375-130 x=245

 Dgeeraj said: (Thu, Jun 16, 2011 04:29:25 AM) Nusrat has right formula to solve this.

 Mathsfobia said: (Sun, Aug 14, 2011 01:59:33 PM) Nice explanation survjt.

 Anshul Patel said: (Sun, Aug 14, 2011 08:56:49 PM) Amasing solutions and discussion by you guys but 1 thing I got in mind while coming through few examples is that if some1 is new in solving this type of problems then please draw 1 rough imaginary sketch and then try to solve this type of examples I prefer it to be more easy.

 Viji said: (Sun, Aug 28, 2011 01:30:42 PM) Vijay kumar your explanation is quite simple and understandable. Thank you.

 Subramanyam Subbu said: (Sat, Sep 3, 2011 11:55:47 PM) distance=speed*time assume length of bridge as x meters here distance=(length of bridge+length of train) x+130=45*(5/18) [ 5/18 indictes conversion of km/hr to m/sec) we get x= 245 m i.e length of the bridge

 Vinu said: (Sat, Sep 24, 2011 08:50:05 AM) I've a doubt, if the bridge length is greater than the length of the train, then the train need to travel twice it's length + (bridge length-train length) to cross the bridge, why that factor is not considering in this problem?

 Ritesh said: (Sat, Oct 1, 2011 11:46:57 PM) I want to ask a simple question, how was to come 25/2 ? please send this answer ASAP.

 Madhu said: (Thu, Oct 13, 2011 08:21:47 AM) We should convert km/hr to m/sec, so we should multiply the 45km/hr by 5/18,then we get 25m/sec.

 Sara said: (Sat, Oct 22, 2011 06:57:28 AM) Total distance of bridge is 45Km/hr*(30/360)hrs =45/12Kms Distance in metres = (45/12)*100 =375 Metres Distance covered = 375M -130M =245M I believe this is the quickest way given the time allocated in such assessments.

 Kriti said: (Sun, Dec 18, 2011 07:54:43 PM) [][][][]```````````````[][][][] ``````````````` Train Bridge Train(and timer (and timer stops here) starts here) <------------------------> This is distance travelled by train in 30 sec (375m) <--------------><--------> Lenght of bridge Lenght of train (130m) Lenght of bridge = distance travelled in 30 sec - lenght of train Hence proved. : )

 Kriti said: (Sun, Dec 18, 2011 08:00:13 PM) @VINU Exactly that would be the total distance travelled by train in 30 sec

 Balurajasekaran said: (Sun, Dec 18, 2011 08:18:15 PM) 45 km/hr = 12.5 m/s then the train travel 375 m in 30 seconds [i.e] 12.5[speed] * 30[total time to reach] = 375[this is the time the train completely out of the bridge] then the length of bridge is 375 - 130[length of train]= 245

 Shahul Hameed.M said: (Sat, Dec 24, 2011 03:50:19 PM) Am telling the easy way to solve this problem...... in basic formula is L=speed*time here we wanna 2 find length of the bridge so, L1+L2=speed *time(L1=length of the train,L2=length of the bridge)v can get d ans easily....

 Mayu said: (Mon, Jan 9, 2012 12:06:17 PM) Yes shahul I like your tact to solve this problem.

 Umesh said: (Thu, Jan 26, 2012 03:24:57 PM) HI All, Let's simplify this: Distance traveled(d) = speed(d) * time(t) taken to travel that distance(d) Speed is 45km/h. Since answer needs to be in meter, let's convert Km/h into m/sec. so, 45*(1000/3600), because 1km=1000mtr and 1hr= 3600sec(60minutes*60 sec per minute). So, our m/sec speed(s) comes to be 45*(5/18)=25/2mtr per sec. We have s = 25/2m/sec and t= 30 secs. so d = s*t =375mtr. Since train itself is 130mtr long it wouldn't travel all 375mtr. So, the distance actually traveled(bridge length)by train is 375mtr- 130mtr = 245mtr. hope this helps.

 Sasha said: (Thu, Feb 16, 2012 05:46:35 PM) Hi coolburn its nice explanation

 Theinternetguy said: (Wed, Apr 18, 2012 11:01:17 AM) Is 45 km/hr relative speed between the bridge and the train?

 Arundeep said: (Wed, May 16, 2012 05:05:22 PM) First of all arragne them in D= ST. S = D/T or T = D/S.

 Mohan said: (Wed, Jun 20, 2012 09:50:39 PM) This problem is very easy to solve speed(v) of train=45km/hr length of train(d)=130m time(t)=30sec d=v*t d=(45*5/18)*30 d=(25/2)*30 d=375 length of bridge(x)=d-length of train x=375-130 x=245m

 Vikram said: (Thu, Jul 26, 2012 03:02:02 PM) Here, A Train 130meter long. Speed of train=45km/hr=45000m/3600sec=12.5m/sec. Within 30sec that train cross distance=12.5m/sec*30sec=375m/30sec. So,Length of Bridge=Cross distance - length of Train =375-130=245Meters. Therefore , The Length of Train= 245Meters.

 Nil said: (Wed, Aug 1, 2012 06:02:23 PM) Given: 1. Length of the train = 130 m 2. Speed of the train = 45 km/hr or (25/2) m/s 3. Time taken by the train to cross bridge = 30s Find: Length of the bridge = x meter First, convert speed of the train from km/hr into m/s So, speed of the train in m/s = [45*(5/18)] km/hr = (25/2) m/s Now, Distance(or length) = speed * time But,Distance = (Length of the bridge + Length of the train) = speed * time Distance = x + 130 = (25/2) * 30 x+130 = 375 x = 375 - 130 Length of the bridge = 245 m

 Pulak said: (Sat, Aug 25, 2012 12:09:00 PM) Thanks Nil.

 Chethan said: (Mon, Aug 27, 2012 08:46:05 PM) dis=len of train+bridge length(take a bridge as x) 130+x speed=45km/hr=45*5/18=25/2 time=30sec dis=speed*time 130+x=25/2*30 130+x=375 x=245m.

 Karthick said: (Fri, Aug 31, 2012 11:46:05 AM) Formula is = (Length of the train + Length of the object)=(Speed of the train* Time of the object).

 Sushi said: (Tue, Sep 25, 2012 07:36:43 PM) HEY. I have a doubt. The length of train is already covering some length of the bridge. Then why we consider both lengths separately?

 Mano said: (Thu, Nov 15, 2012 01:37:10 AM) Your are right sushi. Please help why we consider both lengths separately? If the train is crossed 130m length in 10 sec it also covered length of bridge? Why we are again consider the bridge length? The train is already crossed the bridge in 10 sec. So the length of the bridge also covered.

 Shoeb said: (Wed, Nov 21, 2012 08:43:58 PM) Formula :- Distance=Speed/Time Answer's in option are given in meter, that mean we can go for 5/18 ready made formula of converting km/hr to m/sec. * 45 x 5/18 = 12.5 (for 1 second ) * 12.5(sec) x 30(sec)given = 375 * 375-130 (given )= 245.

 Parthiban said: (Tue, Nov 27, 2012 08:30:08 PM) Easy to find no need to put x and y. 45000m/360seconds = 125 mps. 30 seconds so, crossing bridge. 30*125=375m. Subtract the train meter : 130m. Answer : 375-130=245m.

 Srikant Kumar said: (Tue, Feb 26, 2013 01:50:54 AM) Best Answer could be for new person: 3600 sec me 45000 meter. 1 sec me 45000/3600 12.5 meter/sec. 30 sec me 12.5*30 = 375 meter. Train length is 130 meter . Bridge length will be :-375-130 = 245 meter.

 Monika said: (Sat, Mar 16, 2013 03:12:39 PM) You can do this without any variable: 45 km/hr*5/18 = 25/2 m/s. Total distance = 25/2*30 = 375. Length of bridge = 375-130 = 245m.

 Rohit said: (Thu, May 23, 2013 04:24:38 PM) Please help me, When the train crosses the bridge, shouldn't we consider the length of the train after the bridge also. All above solutions are only by considering the start point of the train. And if only that is considered then what is the use of the length of the train.