Answer:
There are two equivalent formulas to choose from when solving work-rate problems. If two people are working together on a job then their work rates add and they can perform the job working together in a shorter amount of time. If we let x = the time it takes a person to complete a task then his work rate is 1/x. In other words, he can complete the 1 job in x number of hours. If we let y = the time it takes a second person to complete the task and t = the time it takes for both people working together we get the following work-rate formulas: