working at their respective constant rates , machine a makes 100 copies in 12 minutes and machine b makes 150 copies in 15 minutes . if these machines work simultaneously at their respective rates for 30 minutes , what is the total number of copies that they will produce ?
machine a can produce 100 * 30 / 12 = 250 copies and , machine b can produce 150 * 30 / 15 = 300 copies total producing 550 copies . c is the answer
multiply(add(divide(100, 12), divide(150, 15)), 30)