One custodian cleans a suite of offices in 3 hours. When a second worker is asked to join the regular custodian, the job takes only 2 hours. How long does it take the second worker to do the same job alone?
1/3 + 1/s = 1/2 s = time for second alone, solve for s
1/s = 1/2 - 1/3
1/s = 1/6
s= 6 hours