anuanwesh   9 years AGO

its a relative speed prblm
total distance =138+102=240
speed=40+32=72
so( 240)%72*5/18=12secs

Like? Yes (11) | No   

asim   9 years AGO

If we consider one train as stationary than distance needed to clear both trains is either 108 m or 132 m.
But both trains are moving in opposite direction,
therefore total clear distance = 108 m + 132 m = 240 m.
also by relativity concept we know that ,
effective speed of train = 40 km / h + 32 km / h = 72 km / h
converting speed in m/sec , we get
speed = 72 * 5 /18 m/sec = 20 m / sec.

now , time taken = distance / speed sec
= 240 m / 20 m/sec
= 240 / 20 sec
= 12 sec .......................ANS

Like? Yes (8) | No (1)  

Debraj Ghosh   9 years AGO

Total length=(132+108)=240m
total speed=(40+32)=72km/h=20m/sec
total time=(240/20)=12 sec

Like? Yes (8) | No (2)  

aman aditya   9 years AGO

total distance=108+132=240m
speed=32+40=72km/hr
=20m/s
tome=240/20=12 s

Like? Yes (6) | No   

ABHINAV PUSHPAM   9 years AGO

Relative speed when trains are in opposite direction = 32+40 = 72 km/hr = 20 m/s

=> Time = 132+108/20 = 240/20 = 12 sec

Option 4)

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manikanta mitta   9 years AGO

relative speed = 32+40 =72 kmph

speed = distance /time

distance =( sum of lengths of two trains)= 240 mts

speed = 72 kmph= 72 * (5/18) mps

t= 12s

Like? Yes (3) | No   

Devendra Marghade   9 years AGO

Relative speed=32+40 Km/hr=72000 m./3600 sec.
So trains has to cross 132+108=240 m. to clear each other, So time required=240/(72000/3600)=12 sec.
Answer is option (4)

Like? Yes (3) | No   

Math Lovers   9 years AGO

Total Length = 108+132 = 240 m

as they are travelling in same direction,
so total speed = 40+32 =72 km/h = 20m/s

hence total time = 240/20 = 12 sec

Like? Yes (2) | No   

Fazila begum   9 years AGO

If two trains are moving in opposite direction,we find relative speed by adding the two train speeds.speeds are 32km/hr and 40km/hr.Relative speed=32+40=72 km/hr.distance and time in option are represented as m and s respectively.so convert km/hr into m/s by multiply with 5/18.72*5/18=20 m/s.Two trains has two different lengths,add them also.therefore,time taken=length of both trains/relative speed.T=(132+108)/20.T=240/20=12s.

Like? Yes (2) | No   

manju   9 years AGO

total distance= 132+108=240m
total speed=32+40=72*5/18=20m/sec
time=distance/speed=240/20=12sec

Like? Yes (3) | No (1)  

Supriya Mondal   9 years AGO

Two trains has to cover 108+132=240 m
Their relative speeds =40+32=72 km/hr
So time needed to cover 240 m is=(3600/72000)*240
=12 sec
So, option 4)12 sec is the right answer

Like? Yes (3) | No (2)  

v v shyam kumar   9 years AGO

relative speed=sum of lengths /time taken.
time taken to cross=240m/32*40 kmph,
240*18/72*5=12 sec.

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Mehul D Parmar   9 years AGO

relative speed=32+40=72kmph

now 72*5/18=20m/s

time taken to cover distance=132+108=240

140m at 20 m/second=240/20=12 second

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NITISH KUMAR   9 years AGO

relative speed=(32+40)=72 kmph
=72*5/18=20 m/sec
time taken=(132+108)/20=12 sec.

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shivaprabhu   9 years AGO

Total Distance to cover by Both trains is =132+108
=240m

total speed =32+40
=72km/hour


therfore time T =240/(72*1000/3600)
T=12 sec

Like? Yes (1) | No   

sompon temtheerakij   9 years AGO

speed = 32+40 = 72 km/hr
distance = 132+108 = 240 m.
time = 240*60*60/72000 = 12 sec

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kranthi kanchanapally   9 years AGO

distance covered is=132+108=240
speed is=32+40=72*5/18=20
so time is=240/20=12 sec

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Thilaka Elangovan   9 years AGO

time taken = sum of the two trains/sum of their speeds
=240m/20m/s
=12s

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Yathiraj   9 years AGO

Because both the trains are travelling in opposite direction,
the relative speed = 32KMPH + 40KMPH = 72KMPH => 20meters/second
Total distance to cross to clear off each other = 132 meters + 108 meters => 240 meters
Time required to travel 240 meters at speed of 20 meters/second
=> 240/20 => 12 seconds.

Option 4.

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Surendhar Ramanujam   9 years AGO

40+32=72kmph; (72*(5/18))= 20m/s; 132+108=240; 240/20=12sec

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Testing Account   9 years AGO

if length of first train:L1
length of second train:L2....time to cross each other is.(L1+L2)/relativespeed

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chandan goswami   9 years AGO

their relative speed will be=40+32=72km/h=20m/sec

total distance =132+108=240m

total time=240/20=12sec

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mohita verma   9 years AGO

relative speed=(32+40)kmph=72x5/18=20m/s
total distance=132+108=240m
time=240/20=12sec

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ankita yadav   9 years AGO

Relative speed=32+40=72km/hr=20m/sec
total distance=132+108=240m
time=distance/speed=240/20=12sec

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Mani Sachdev   9 years AGO

total relative speed= 72 km/hr=20 m/sec
total time taken by train 132+108=240 m
finally 240/20=12 sec

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B.venkata suresh   9 years AGO

time=(distance/speed)
32 km/hr=32*5/18 m/sec
40 km/hr=40*5/18 m/sec
then
time = (132+108/20)=12 sec

Like? Yes (1) | No   

swetha   9 years AGO

time=distance/speed
32km/hr=3*5/18m/sec
40 km/hr=40*5/18m/sec
time=132+108/20=12sec

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krishna chandrika   9 years AGO

relative speed = 32+40=72kmph=72*(5/18) = 20m/s
total distance=132+108 = 240m
time=d/s
=240/20
=12sec

Like? Yes (1) | No   

akshay kumar   9 years AGO

add the speed of both trains by converting them into msec and also add the length of both the trains .
now divide total length by total speed required time will come out.

Like? Yes (1) | No   

RAKESH ARYA   9 years AGO

total taken time = ( ((132+108)/1000)/(32+40))*60*60 sec.
= 12 sec.

Like? Yes (1) | No   

Chirag Jindal   9 years AGO

Respective speeds are 160/18 and 200/18 m/s.
Therefore relative speed=u+v=20m/s
Total distance=108+132=240m

Hence time=240/20=12sec

Like? Yes (1) | No   

NESAB JAFAR   9 years AGO

train relative speed =72kmph=20m/s
lenght =108+132=240
tiime=240/20
time=12 second

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Lavanya Rajendran   9 years AGO

240=72*5/18*t

t=240/20
t=12

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puja   9 years AGO

travelling in opposite direction so total speed=32+40=72km/h
total length=132+108=240m
speed=distance/time
time=240*60*60/1000*72
12sec

Like? Yes (1) | No   

rajat   9 years AGO

Same direction s1+s2
32+40=72 Km/hr
72 km/hr=20 m/s
And
train moves toward each other so distance=108+132
=240 m
So, time=distance/speed
t=240/20=12sec
So time take is 12 sec

Like? Yes (1) | No   

Ayan Patra   9 years AGO

Distance = 108 + 132 = 240 m

Relative speed = 32 + 40 = 72 km/hr = 20 m/s

Time = distance/speed = 240 / 20 = 12 s.

Like? Yes (1) | No   

Divyansh jaiswal   9 years AGO

total distance=240m
speed=20m/sec
time taken=240/20=12sec

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vimal tiwari   9 years AGO

sum of speeds (toward)=32+40=72 Km^2/hr
total distance=108+132=240 m
time=(240/72) =10/(3*5/18)=12 sec

Like? Yes (1) | No   

ammar   9 years AGO

Distance to be travelled = 132 + 107 = 240m
Relative velocity of one train with respect to another = 32-(-40) = 72 km/h = 20 m/s
Time taken to clear off = 240/20 = 12 s.

Like? Yes (1) | No   

kiruthika   9 years AGO

time=distance/speed
time=(132+108)/((32+72)*5/18)
time=12 sec

Like? Yes (1) | No   

KARTHIKA.N   9 years AGO

time=d/s
time=(132+108)/(32+40)*5/18
time=12 sec

Like? Yes (1) | No   

Hemalatha   9 years AGO

relative speed of the train = 72km/hr i.e 20m/sec. Now the time taken to cross(132+108) 240m = 240/20=12sec.

Like? Yes (1) | No (1)  

k sureshbabu   9 years AGO

here trains speed should be additive so speed is=72kmph

means =20mps(72000/3600)
total distance is 132+108=240meters
so time taken to complete 240meters is 12sec

Like? Yes (1) | No (1)  

ADERU CHENCHU NITHISH   9 years AGO

time t= (132+108)/((32*5/18)+(40*5/18))
=240/((80/9)+(100/9))=240*9/180=12 sec

Like? Yes (1) | No (1)  

UDIT   9 years AGO

(speed of 1st train + speed of 2nd train)*time(?)=(length of 1st train + length of 2nd train) =(240*18)/(72*5)=12 sec.(option 4)

Like? Yes (1) | No (1)