The production line where you work can assemble 5 amplifiers every 30 minutes. At this rate, which correctly calculates the number of hours it takes to assemble 230 amplifiers?
5 amplifiers in 30 minutes is the same as 10 amplifiers per hour. Divide 230 amplifiers by 10 amplifiers (which is how many you can make per hour) to get 23 hours [the answer].
