working alone , printers x , y , and z can do a certain printing job , consisting of a large number of pages , in 12 , 20 , and 20 hours , respectively . what is the ratio of the time it takes printer x to do the job , working alone at its rate , to the time it takes printers y and z to do the job , working together at their individual rates ?
"p 1 takes 12 hrs rate for p 2 p 3 together = 1 / 20 + 1 / 20 = 1 / 10 therefore they take 10 ratio = 10 / 1 = d"
divide(12, divide(const_1, add(divide(const_1, 20), divide(const_1, 20))))