5 pumps , working 9 hours a day , can empty a tank in 3 days . how many hours a day should 6 pumps work in order to empty the tank in 1 day ?
"let the required hours needed be x more pumps , less hours ( indirect proportion ) more days , less hours ( indirect proportion ) hence we can write as ( pumps ) 5 : 6 } : : x : 9 ( days ) 3 : 1 = > 5 * 3 * 9 = 6 * 1 * x = > x = 45 / 2 = > 22.5 answer : b"
divide(multiply(multiply(5, 9), 3), 6)