A lake contain 900 gallons of water. The city is pumping water into the lake at a rate of 30 gallons per minute. Which expression represents the amount of water in the pond, in gallons, after 12 minutes?

The sum of the reciprocal of a positive number and the reciprocal of 2 more than the number is 3/4 equation: the number is

Siri can type 90 words in 40 minutes about how many words would you expect her to type in 10 minutes at this rate

Aprisoner is trapped in a cell containing three doors. the first door leads to a tunnel that returns him to his cell after two days of travel. the second leads to a tunnel that returns him to his cell after three days of travel. the third door leads immediately to freedom. (a) assuming that the prisoner will always select doors 1, 2 and 3 with probabili- ties 0.5,0.3,0.2 (respectively), what is the expected number of days until he reaches freedom? (b) assuming that the prisoner is always equally likely to choose among those doors that he has not used, what is the expected number of days until he reaches freedom? (in this version, if the prisoner initially tries door 1, for example, then when he returns to the cell, he will now select only from doors 2 and 3.) (c) for parts (a) and (b), find the variance of the number of days until the prisoner reaches freedom. hint for part (b): define ni to be the number of additional days the prisoner spends after initially choosing door i and returning to his cell.