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An escalator moves downward from street level to a subway

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An escalator moves downward from street level to a subway

by AAPL » Fri May 11, 2018 6:08 am

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An escalator moves downward from street level to a subway platform at a constant rate. When the escalator is turned off, Wesley takes 70 steps to descend from street level to the platform. When the escalator is turned on, Wesley needs only 36 steps to descend from street level to the platform. If Wesley begins at the platform and walks upward, against the escalator's downward movement, how many steps will he need to take to reach street level? (Assume that Wesley walks at a constant rate in all scenarios.)

A. Between 50 and 100 steps
B. Between 100 and 200 steps
C. Between 200 and 500 steps
D. Between 500 and 1000 steps
E. Over 1000 steps

The OA is E.

Is there a strategic approach to this question? Can anyone help, please? Thanks in advance!
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subway

by GMATGuruNY » Fri May 11, 2018 6:31 am
AAPL wrote:An escalator moves downward from street level to a subway platform at a constant rate. When the escalator is turned off, Wesley takes 70 steps to descend from street level to the platform. When the escalator is turned on, Wesley needs only 36 steps to descend from street level to the platform. If Wesley begins at the platform and walks upward, against the escalator's downward movement, how many steps will he need to take to reach street level? (Assume that Wesley walks at a constant rate in all scenarios.)

A. Between 50 and 100 steps
B. Between 100 and 200 steps
C. Between 200 and 500 steps
D. Between 500 and 1000 steps
E. Over 1000 steps
DOWNWARD:
When the escalator is turned OFF, the number of steps taken by Wesley to travel downward = 70.
When the escalator is turned ON, the number of steps taken by Wesley to travel downward = 36, implying that the number of downward steps attributed to the escalator = 70-36 = 34.
Implication:
For every 36 steps taken by Wesley, the escalator moves downward 34 steps.

UPWARD:
For every 36 steps Wesley takes UPWARD, the escalator will move him DOWNWARD 34 steps, with the result that the net movement upward = 36-34 = 2 steps.
In other words, 36 upward steps taken by Wesley = a net upward movement of 2 steps.
Since Wesley must travel upward a total of 70 steps, we can set up the following proportion:
(36 upward steps taken by Wesley)/(net gain of 2 steps) = (x upward steps taken by Wesley)/(70 steps)
36/2 = x/70
18 = x/70
x = 18*70 = 1260.

The correct answer is E.
Last edited by GMATGuruNY on Sun May 31, 2020 3:00 am, edited 1 time in total.
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by Scott@TargetTestPrep » Mon May 14, 2018 4:05 pm
AAPL wrote:An escalator moves downward from street level to a subway platform at a constant rate. When the escalator is turned off, Wesley takes 70 steps to descend from street level to the platform. When the escalator is turned on, Wesley needs only 36 steps to descend from street level to the platform. If Wesley begins at the platform and walks upward, against the escalator's downward movement, how many steps will he need to take to reach street level? (Assume that Wesley walks at a constant rate in all scenarios.)

A. Between 50 and 100 steps
B. Between 100 and 200 steps
C. Between 200 and 500 steps
D. Between 500 and 1000 steps
E. Over 1000 steps
Since Westley takes 70 steps to descend on the escalator when it's turned off, we see that the escalators has 70 steps.

We also see that the escalator provides an extra 70 - 36 = 34 steps when it's turned on. However, this really means for every 36 steps Wesley is moving (upward or downward), the escalator is moving downward 34 steps. Therefore, when he is moving upward 36 steps, the escalator is working against him 34 steps. So he only has a net rate of 36 - 44 = +2 steps for every 36 steps he is moving upward on the escalator.

Since the escalator has 70 steps and 70/2 = 35, he needs to walk 36 x 35 = 1,260 steps upward on the escalator in order to reach street level from the platform.

Answer: E

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