Question 520556
With job problems like this, it is best to look at the problem as a question of fractions.
.
a crew of 5 workers can build a barn in 9 days
the crew builds 1/9 of the barn per day
each worker is 1/5 of the crew
each worker builds 1/45 of the barn per day
.
5 workers * 1/45 barn/day * 9 days = 45/45 barn = 1 barn
.
3 workers * 1/45 barn/day * x days = 1 barn
3 * 1/45 * x = 1
3/45*x = 1
3x = 45
x = 15 days
.
Done.