A pipe can fill a reservoir in 20 hr. A drainage pipe can drain the reservoir in 30 hr. How long would it take to fill the reservoir if the drainage pipe were left open by mistake? (Hint: The rate at which water drains should be negative.) Write your answer as an
integer, simplified fraction, or mixed number.
It will take
hr to fill the reservoir.

Over the course of the school year, you keep track of how much snow falls on a given day and whether it was a snow day. your data indicates that of twenty-one days with less than three inches of snow, five were snow days, while of the eight days with more than three inches of snow, six were snow days. if all you know about a day is that it is snowing, what is the probability that it will be a snow day?