Escalator problem

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Incognito
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solution to the above problem

speed of man= M
speed of escalator=E
distance =d --constant

speed = distance/time

M+E=d/30                 ----speed of both man and escalator moving in the same direction. Takes less                                                time.

M-E=d/90                  ----speed of both man and escalator moving in the different direction. Takes                                                    more time.Speed of man has to be greater than speed of escalator and 
                                         therefore M-E=+ve.

add both the equations

2M=4d/90

M= d/45

speed of man(M) = distance(d) / time(45)

therefore man takes 45 secs to travel the distance d

Incognito
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Answer is 45


Incognito
Incognito's picture
speed of a=2steps /x

speed of a=2steps /x seconds
speed of b=1step/x seconds
speed of escalator=N step/ x seconds

time taken by A alone to travel 40 steps= 40steps/2steps/x second=20x second
now in this 20 x second time the escalator is also moving with him so in this time when A has covered 40 steps distance covered by escalator is
= N steps/x second * 20 x seconds =20 N steps

total steps travelled =40 by A + 20N by escallator=40 +20 N........1

similarly total stepps in B case is = 30 by B and +30 N by escallator=30+30 N...............2

when escallator will not move total steps travelled by and b will become equal so
40+20N=30+30N
N=2
putting in equation 1 or 2
total steps can be calculated as =60....:)

Incognito
Incognito's picture
Might help

Might help

Incognito
Incognito's picture
the ans is 45 sec's let L be

the ans is 45 sec's

let L be the distance he shud travel and v be his speed and v1 be speed of esc
then u get
L-v1*30=v*30
then when movingg down
L+v1*90=v*90

then for 3rd case v1=0
so
L=v*t

solve this

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