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I am in the habit of walking up the subway escalator while it is running. I climb 20 steps at my normal pace and it takes me 60 seconds to reach the top, whereas my wife climbs only 16 steps and it takes her 72 seconds to reach the top. If the escalator broke down tomorrow, how many steps would I have to climb?

Guest May 10, 2015

Best Answer 

 #1
avatar+223 
+15

s=total numbers of steps

v= velocity of the escalator  (steps/seconds)

make two different equation with the info given in the text. "Mr anonumous" climbs 20 step by his own, the escalator helps him with v*60 steps. "Mrs anonymous" climbs 16 steps by her own, the escalator helps her with
v * 72 steps.

(1)  s=20+60v

(2)  s=16+72v

(1)------> v=(s-20)/60

now use the "new"(1) and put that one into equation number 2.

s=16+72*(s-20)/60     72/60=6/5 therefore multiplie everything with 5

5s=80+6(s-20)----> 5s=80+6s-120

5s-6s=80-120

s=40

"Mr anonymous"have to climb 40 steps instead of 20 if the escalator breaks down.

Headingnorth  May 10, 2015
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3+0 Answers

 #1
avatar+223 
+15
Best Answer

s=total numbers of steps

v= velocity of the escalator  (steps/seconds)

make two different equation with the info given in the text. "Mr anonumous" climbs 20 step by his own, the escalator helps him with v*60 steps. "Mrs anonymous" climbs 16 steps by her own, the escalator helps her with
v * 72 steps.

(1)  s=20+60v

(2)  s=16+72v

(1)------> v=(s-20)/60

now use the "new"(1) and put that one into equation number 2.

s=16+72*(s-20)/60     72/60=6/5 therefore multiplie everything with 5

5s=80+6(s-20)----> 5s=80+6s-120

5s-6s=80-120

s=40

"Mr anonymous"have to climb 40 steps instead of 20 if the escalator breaks down.

Headingnorth  May 10, 2015
 #2
avatar+90988 
0

Thanks Headingnorth.   Well done!

This one I definitely want to come back to.   

Melody  May 10, 2015
 #3
avatar+78577 
+10

This is one I pondered on for a little while.....I finally solved it with the same answer as Headingnorth....However, I saw it in a slghtly different manner....

 

The first assumption to be made is that both people step on consecutive steps.....they don't "skip" any steps.

Notice that the man steps on the first step at the bottom, and by the time he gets to the top.....he is on the top step of the escalator.  Thus......there are 20 consecutive steps from the top of the escalator back to the first step that he stepped on.  And between this step  and the bottom of the escalator, we can let this number of steps = s.  So...the total steps on the escalator = 20 + s

 

And the same situation develops for his wife. When she gets to the top of the escalator, there are 16 consecutive steps from the top of the escalator back to the first step she stepped on. But notce.......if "s"  steps were fed by the escalator in 60 seconds from the bottom of the escalator to the man's first step [20 steps from the top], then (6/5)s steps must have been fed by the escalator to the woman's first step [16 steps from the top]. This is because it takes her 6/5 times as long [72 seconds / 60 seconds]  to get from the bottom to the top as it does him.

So....from her point of view....there must be (6/5)s + 16 steps on the escalator......

 

So, since the number of steps are equal in each case.....we have....

s + 20 =  (6/5)s + 16      subtract 16 and s from both sides

4 = (1/5)s       multiply by 5 on both sides

20 = s

 

So there are, in the man's case ....   s + 20   =  20 + 20   = 40 steps showing on the escalator.

Check that   ...    (6/5)(20) + 16  =    24 + 16 = 40 steps in the woman's case, too......!!!!!

 

  

CPhill  May 14, 2015

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