How to solve the following question A man can walk up a moving 'up' escalator in 30s. The same man can walk down this moving 'up' escalator in 90s. Assume that his walking speed is same upwards and downwards. How much time will he take to walk up the escalator, when its not moving? a. 30s b. 45s c. 60s d. 90s Thanks Praks
90 sec is the correct answer
as speed of escalator is twice that of man's
sorry correct ans is 45 sec
speed of man is twice that of escalator's
it can be assumed that speed of man is greater than that of escalator
distance is same v+u = x/30 and v-u = x/90 thus v+u / v-u = 3 or v/u =t then t+1/t-1=3 2t/2=3+1/(3-1) thus t = 2 or speed of the elevator is 2 times the man speed. Now 3u/u=t'/30 or t'=90 sec is answer.
the correct answer is 45 sec..........
as speed x time = distance
so speed is inversely proportional to time
speed of goin up/speed of goin down = time to go down/time to go up
hence speed of goin up = 3 * speed of goin down
now speed of man+speed of elevator = speed of goin up
and speed of man - speed of elevator = speed of goin down
so man's speed is twice the elevator speed
hence
2/3=30/x
whre x is time needed to move up if escalator is stoppd
so x=45
i guess the answer is 90 as it has been asked for time taken by man to walk on the escalator which is stagnant......if it would have been asked for the time taken by escator then the answer might be 45 sec....
There is no question of the option d, as it logically points that his speed should be less than 90 and more than 45 so either b or c is correct :P
The solution according to me is correct. (for and to be 45sec)
let the speed of man = U
let the speed of esc = v
D/(u+v)=30
D/(u+v)=90
u=2v
Implies, D/(3v)=30 (i,e, v=D/90)
now, v=0
D/U=D/2v=45 sec
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1)--it take 40 steps to climb up a moving escalator and 60 secs to move down same moving up escalator . how long will it take for him to move up the escalator when it is switched off??
2)--A and B are in a shopping complex . they found an escalator that is moving up at a constant speed . both use the escalator to climb up but instead of letting the escalator do to complete work, they walk up the escalator at different speeds.A has a walking speed twice that of B. A reaches the top of the escalator after having climbed 40 steps while B takes only 30 steps to reach the top. if the escalator was turned off , how many steps would A have to take to walk up(in steps)????
PLZZZZZZ help me i stuck into this !!!!!!!!!
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
Might help
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....:)