ashubha mishra

• Jan 19th, 2006

 

trains r moving in same direction so their crossing length will be 200-100=100m.so the crossing velocity will be100/30=33.3s

chandra sekhar

• Jan 19th, 2006

 

time taken to cross to trains when moving in same directionis (200+100)/(a-b)=30in opposite directions (200+100)/(a+b)=20a-b=10a+b=15a=12.5 and b=7.5

gt_hotin

 Profile Answers by gt_hotin 

• Feb 26th, 2006

 

l1=200;

spped of l1 be v1;

l2=100;

speed of l2 be v2;

200/v1+100/v2=30;

200/v1-100/v2=20;

hence

v1=8 and v2=20

sridhar

• Mar 6th, 2006

 

200+100/(a-b)=20;   a-b=15;

200+100/(a+b)=10;  a+b=30;

therefore a=22.5  b=7.5

vkparthipan

• Jun 19th, 2006

 

time taken to cross to trains when moving in same directionis 

so u have to add two sppeeds(200+100)/(a-b)=30in

 opposite directions so u have to subtract the two speds(200+100)/(a+b)=20a-b=10a+b=15a=12.5 and b=7.5

guys don t confuse thi s  is correct one..........

ankur kohli

• Jul 21st, 2006

 

wen moving in same direction

300=(x+y)30

in opp direction

300=(x-y)20

on solving for x and y v get

x=12.5,y=2.5

srinivas

• Jul 22nd, 2006

 

d1=200

d2=100

if they r in same direction then relative speed is=(200-100)/30=10/3=3.33

if they r in opposite direction then relative speed is=(200+100)/20=300/20=15

Kripal

• Sep 4th, 2006

 

Let Length of train 1=L1=200m,  Length of train 2=L2=100m

Let Speed of train 1=V1=? , Speed of train 2=V2=?

Dont confuse with the total crossing length. Its always (200+100=300m). You can easily visualize it supposing one of the trains is not moving.

Now

Relative velocity of train 1 w.r.t train 2 when moving in same direction =     V1-V2 =300/30=10 m/s

Relative velocity of train 1 w.r.t. train 2 when moving in opposite direction = V1+V2 =300/20=15 m/s

Solving for V1 & V2

we get V1=25/2 m/s = 45Km/hr & V2=5/2 m/s = 9Km/hr

ramraj meena

• Dec 29th, 2006

 

guys.....its very simple quest.....i don't know y u confusing so much.........as ankur kohli solved is rightanswer 12.5 and 2.2

padmanjali

• Jan 19th, 2007

 

hi

(200+100)/(u-v) =30 same direction

(200+100)/(u+v)= 20 oppsite direction

 Solve carefully uwill get  u =12.5 v=2.5

abhilash

• Jul 21st, 2007

 

any way we want to cover a distance of 300m
in first case the time is 30 s.
therfore v1+v2=300/30        (v1-> actual velocity of first train and v2 the others )
ie  v1+v2=10
in 2 nd case
v1- v2=300/20
ie v1 - v2=15.
therefore v=12.5 and v2=2.5

deepasaha

 Profile Answers by deepasaha 

• Jul 29th, 2007

 

Let u m/s and vm/s be the speeds of the trains resp.

When trains r moving in d same direction

u-v=300/30=10............(1)

Whn trains r moving in d opposite directions

u+v=300/20=15...........(2)

solving equations 1 and 2 we get

u=12.5m/s and v=2.5m/s

prem75tigkiit

 Profile Answers by prem75tigkiit 

• Oct 17th, 2007

 

suppose the speed of the trains be x and y.
to cross one another they must have to cover the sum of their length whether in opposite or same direction. but in case of opposite direction there covered distance will be summed up and In same direction the subtracted value is the length.

so here when in same direction the distances covered by the trains are 30x and 30y which is equal to 300 m. if subtracted.
so
30x-30y=300 or x-y=10
in case of opposite direction it is 20x+20y=300 or x+y=15
hence we get 2x=25 or x=12.5
and then y=2.5.

so the speed are 12.5m/s and 2.5 m/s.

prakash

• Nov 18th, 2007

 

as per the two equations generated ,    a - b = 10  ---------------(1)
                                                               a + b = 15 ---------------(2)

                                        a = 12.5
                                        b = 2.5
 
               most of them did the same mistake that a = 12.5    and b = 7.5

that is the wrong one and the correct answer is  a = 12.5   , b = 2.5

Debu144

 Profile Answers by Debu144 

• May 26th, 2008

 

let,
100m train => speed a
200m train => speed b

same direction: 300/(a-b)=30            => a-b=10
opposite direction: 300/(a+b)=20      => a+b=15

Solving the equations: a=12.5m/s; b=2.5m/s

arunmscit86

 Profile Answers by arunmscit86 

• Jun 28th, 2008

 

22.5 and 7.5