Officials begin to release water from a full man-made lake at a rate that would empty the lake in 18 weeks, but a river that can fill the lake in 30 weeks is replenishing the lake at the same time. How many weeks does it take to empty the lake? Express your answer as a fraction reduced to lowest terms, if needed.

1. why is a frequency distribution useful? it allows researchers to see the "shape" of the data. it tells researchers how often the mean occurs in a set of data. it can visually identify the mean. it ignores outliers. 2. the is defined by its mean and standard deviation alone. normal distribution frequency distribution median distribution marginal distribution 3. approximately % of the data in a given sample falls within three standard deviations of the mean if it is normally distributed. 95 68 34 99 4. a data set is said to be if the mean of the data is greater than the median of the data. normally distributed frequency distributed right-skewed left-skewed