SOLUTION: Hi. I don't understand how I'm supposed to solve this problem. Could you please clearly explain how to set it up and solve it ...thank you. The time is takes to build a skyscrap

Algebra ->  Proportions  -> Lessons -> SOLUTION: Hi. I don't understand how I'm supposed to solve this problem. Could you please clearly explain how to set it up and solve it ...thank you. The time is takes to build a skyscrap      Log On


   

Question 708576: Hi. I don't understand how I'm supposed to solve this problem. Could you please clearly explain how to set it up and solve it ...thank you.
The time is takes to build a skyscraper is proportional to its height and inversely proportional to the number of construction workers. If it takes 10 workers 2.5 years to build a 20 story building, how long will it take 40 workers to build a 120 story building?
_______ years
Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
The basic description is like this, using t for time, h for height, w for workers, and k is a proportionality constant. The description is t=k%28h%2Fw%29.

10 workers 2.5 years to build a 20 story building : lets you determine k.
t%2A%28w%2Fh%29=k, so substituting, k=2.5%2810%2F20%29, k=1.25.

You now know, t=1.25%28h%2Fw%29.

how long will it take 40 workers to build a 120 story building?
Just plug in the values.
t=1.25%28120%2F40%29=1.25*3=4
t=4 years.