Sally can address a box of envelopes in 30 minutes Her brother Jim can address a box of envelopes in one hour period how long will it take both working together to address a box of envelopes?

Sally can address a box of envelopes in 30 minutes, which means she works at a rate of 2 boxes per hour. Jim can address a box in 60 minutes, or 1 box per hour. Working together, their combined rate is 2 + 1 = 3 boxes per hour. Therefore, it will take them ( \frac{1}{3} ) of an hour, or 20 minutes, to address one box of envelopes together.