SOLUTION: The elevator in the Washington Monument takes 75 seconds to travel 500 feet to the top floor. What is the speed of the elevator in miles per hour? Give your answer to two signifi

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Question 153600: The elevator in the Washington Monument takes 75 seconds to travel 500 feet to the top floor. What is the speed of the elevator in miles per hour? Give your answer to two significant digits.
Found 2 solutions by Earlsdon, Edwin McCravy:
Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
You need to convert: 500ft per 75 secs into miles per hour.
To convert ft/sec into mph, you would divide the number of feet by 5,280 feet/mile, and to convert seconds to hours, you would divide the number of seconds by 3,600 secs/hour.
Let's see how this works:
(500 ft)/(75 secs) = (500 ft/5280 ft per mile)over(75 secs/3600 secs per hour)= 4.54 miles per hour.

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!
Edwin's solution:
The elevator in the Washington Monument takes 75 seconds to travel 500 feet to the top floor. What is the speed of the elevator in miles per hour? Give your answer to two significant digits.


%28500ft%29%2F%2875s%29

Now use the fact that 5280ft=1mi to create
a unit fraction to cancel away the ft's.  Since
ft is in the top, we want to create a unit 
fraction with ft on the bottom, so we create
the unit fraction 1mi%2F%285280ft%29. So we multiply
by that fraction:

%28500ft%29%2F%2875s%29x1mi%2F%285280ft%29.

and then cancel away the ft's.

%28500cross%28ft%29%29%2F%2875s%29x1mi%2F%285280cross%28ft%29%29

Now use the fact that 60s=1min to create
a unit fraction to cancel away the s's.  Since
s is in the bottom, we want to create a unit 
fraction with s on the top, so we create
the unit fraction 60s%2F%281min%29. So we multiply
by that fraction:

%28500cross%28ft%29%29%2F%2875s%29x1mi%2F%285280cross%28ft%29%29x60s%2F%281min%29.

and then cancel away the s's.

%28500cross%28ft%29%29%2F%2875cross%28s%29%29x1mi%2F%285280cross%28ft%29%29x60cross%28s%29%2F%281min%29. 

Now use the fact that 60min=1h to create
a unit fraction to cancel away the min's.  Since
min is in the bottom, we want to create a unit 
fraction with min on the top, so we create
the unit fraction 60min%2F%281h%29. So we multiply
by that fraction:

%28500cross%28ft%29%29%2F%2875cross%28s%29%29x1mi%2F%285280cross%28ft%29%29x60cross%28s%29%2F%281min%29x60min%2F%281h%29.  

and then cancel away the min's.

%28500cross%28ft%29%29%2F%2875cross%28s%29%29x1mi%2F%285280cross%28ft%29%29x60cross%28s%29%2F%281cross%28min%29%29x60cross%28min%29%2F%281h%29. 

Now the only units that are not canceled away are mi 
on the top and the h on the bottom.

%28%28500%29%2860%29%2860%29mi%29%2F%2875%29%285280%29h

1800000mi%2F%28396000h%29

4.545454545mi%2Fhr

Rounding to two significant digits:

4.6mi%2Fhr

Edwin