the quantity y varies directly as x and inversely as z. when x is 10 and z is 4, y is 15. what is y when x is 20 and z is 6?
1) 6
2) 20
3) 27
4) 30

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?