one pump, let's call it A, fills the reservoir by 1/60 every hour. Now, B fills it by 1/80 every hour. C empties it by 1/90 every hour. All three are on, so now we combine them into one function: t(1/60 + 1/80 - 1/90) = 1, where t = the time it takes to fill it, and 1 is just our "reservoir finally filled" marker.
isolate t onto one side and we see t = 720/13 exactly, or approximately 55.38 hours. let me know if this is the wrong answer but I'm pretty sure it is correct!
For this case, the first thing to do is find the scale factor. Using the measure of height we have: k = (360) / (18 * (1/12)) k = 240 Thus, the length of the building is: (14 * (1/12)) * (240) = 280 feet Answer: The lenght of the real building is: 280 feet
