Question

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 70 workers to build a 60 story building?

Answer 1

Answer:

$t = 1.07 years$

Explanation:

As we know that time to build is proportional to height and inversely proportional to the number of workers

so we can say that

$t = c\frac{H}{N}$

here we know that 10 workers took 2.5 years to build 20 story building

so we will have

$2.5 years = c\frac{20}{10}$

$c = \frac{2.5}{2}$

now we will have 70  workers to build 60 story building

so we have

$t = \frac{2.5}{2} \times \frac{60}{70}$

$t = 1.07 years$