Question 641403
Inverse variation means that t=k/n where t is time, n is number of people working on the job and k is the constant of proportionality.  First, we need to find the value of k and the problem allows us to do that:
6=k/20
Solving for k, we get:
k=120
Now for our problem:
t=120/30
t=4 hours---time required for 30 people to do the job.

CK
4=k/30
k=120

Hope this helps---ptaylor