working at their respective constant rates , machine a makes 100 copies in 10 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 / 10 = 300 copies and , machine b can produce 150 * 30 / 15 = 300 copies total producing 600 copies . b is the answer"
multiply(add(divide(100, 10), divide(150, 15)), 30)