Trains Boats and Streams Practice Test 4 with solutions

Question : 28 of 40

Marks: +1, -0

Anu is walking at a constant speed halfway between two parallel train tracks. On each track is seen trains of the same length. They approach Anu from different directions both at the same speed of v km/hr. The train going in the same direction as Anu takes

t_1

second to pass her, while the other takes

t_2

seconds to pass her. The speed of Anu (in km/hr) is:

${t_1-t_2}/{t_1+t_2}v$
${t_2-t_1}/{t_1+t_2}v$
${t_1+t_2}/{t_1-t_2}v$
${t_1+t_2}/{t_2=t_1}v$

Validate

Solution:

Let the length of both the trains = l kms
Speed of both the trains = v kmph
Speed of Anu = x kmph
Time taken by the train coming from the opposite direction =

t_2

t_2

l/{v+x]

l =

t_2(+x)

... (i)
Time taken by the train moving in the same direction =

t_1

t_1

l/{v-x}

L =

t_1(v-x)

... (ii)
Equating (i) and (ii), we get

t_2

(v + x) =

t_1

(v - x)

t_2

v +

v_2

x =

t_1v - t_1x

x =

{v(t_1-t_2)}/{t_1+t_2}

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