Question 252693
If 15 men can do a piece of work in 90 days, in how many days can 30 men do the same work?
-------------
Number of men and days to do the job are inversely related.
-------------
Equation:
days = k/number of men
---
Solve for "k":
90 = k/15
k = 15*90 = 1350
-----
Equation for your problem:
days = 1350/number of men
------
Your Problem: in how many days can 30 men do the same work?
days = 1350/30
days = 45 
=================
Cheers,
Stan H.