There is an elevator in a building that is 450 feet tall with 30 stories. Starting from the 20th floor, the elevator descends steadily toward the bottom floor, passing the 15th floor half a minute after its descent started. The graph below summarizes this information. Based on the graph, determine how fast the elevator travels and the time it would take to go from the 20th floor to the bottom of the building.
https://media.glynlyon.com/g_alg02_ccss_2013/3/img_alg2_3.10_problem25a.gif

Question

There is an elevator in a building that is 450 feet tall with 30 stories. Starting from the 20th floor, the elevator descends steadily toward the bottom floor, passing the 15th floor half a minute after its descent started. The graph below summarizes this information. Based on the graph, determine how fast the elevator travels and the time it would take to go from the 20th floor to the bottom of the building.
https://media.glynlyon.com/g_alg02_ccss_2013/3/img_alg2_3.10_problem25a.gif

mertsj · Answer

How long does it take the elevator to go from 450 feet to 225 feet?

anonymous · Answer

225

mertsj · Answer

Time is the x value.  Look at the x axis.

anonymous · Answer

0.5

mertsj · Answer

Yes.  But I read it wrong.  It goes from 300 ft to 225 feet in .5 seconds.  How many feet is that?

anonymous · Answer

75 feet

mertsj · Answer

So it goes 75 feet in .5 seconds.  How many feet would that be in 1 second?

anonymous · Answer

150 feet

mertsj · Answer

So that is the speed:  150 feet per second.

mertsj · Answer

No.  The time is in minutes so it would be 150 feet per minute.

anonymous · Answer

the time it would take to go from the 20th floor to the bottom of the building.

anonymous · Answer

would be 150 feet per minute from the 20th floor to the bottom?

anonymous · Answer

which is 2 minutes

mertsj · Answer

I don't know what to think about the time units because the problem says it went from the 20th floor to the 15th floor in 1/2 minute but the graph says it went from 300 feet to 225 feet in .5 seconds.

mertsj · Answer

I guess I would go with the minutes since 150 feet in 1 second makes no sense for an elevator.

anonymous · Answer

so the answer would be 2 seconds to the bottom?

mertsj · Answer

2 minutes.  yes.

mertsj · Answer

I guess I would go with the minutes since 150 feet in 1 second makes no sense for an elevator.

anonymous · Answer

2 minutes not 2 seconds.

mertsj · Answer

yes

anonymous · Answer

ok thanks

mertsj · Answer

yw.  And you might point out the discrepancy in the units to your teacher.

anonymous · Answer

Wait, so i would say it travels 350 feet in 2 minutes to go from the 20th floor to the bottom of the building?

mertsj · Answer

Wait.  The problem asks two questions.  What is the first question?

anonymous · Answer

Based on the graph, determine how fast the elevator travels. 2nd question, and the time it would take to go from the 20th floor to the bottom of the building.

mertsj · Answer

How fast does the elevator travel?

anonymous · Answer

150 feet per minute?

mertsj · Answer

Yes.  That is the answer to the first question.

mertsj · Answer

2nd question:  How long does it take the elevator to get from the 20th floor to the bottom?

anonymous · Answer

2 minutes?

anonymous · Answer

no, 2 minutes and 30 seconds?

mertsj · Answer

20th floor to 15th floor:  .5 minutes
15th floor to 10th floor:  .5 minutes
10th floor to 5th floor:  .5 minutes
5th floor to bottom floor:  .5 minutes.
I'll leave it to you to add them all up.

triciaal · Answer

a simplier approach
450 ft with 30 stories = 9ft/floor
from 20 to 15 in 1/2 min = 5.9 = 45 ft in 1/2 min
20 floors to bottom = 20 (9) = 180 ft
set up ratio  let t = time
45:1/2 = 180/t  t=2mins

anonymous · Answer

thanks

triciaal · Answer

oops i have a calculation  error 450/30 = 15 but the method is correct

triciaal · Answer

rate = 150 ft/min ; it would take 2 mins from 20th floor to bottom