Answer:
Step-by-step explanation:
This is an inverse proportion.
men = k / Time So first we need to find k
k = men * Time Substitute values
k = 15*80
k = 1200 Notice the units are man days.
Now what happens if we increase the number of men to 20? What happens to the number of days.
20 = 1200 / time Multiply both sides by time
20*time = 1200 Now divide by 20
time = 1200/20
Answer: time = 60 days
