one copy machine can make 20 copies a minute , and a second copy machine makes 10 copies a minute . if the two copiers work together , how long would it take them to make 900 copies ?
"total work done by both machines in a minute = 20 + 10 = 30 copies total number of copies required = 900 time = 900 / 30 = 30 mins answer d"
divide(power(10, const_3), add(20, 10))