Fred and John want to paint Fred's motorboat. Fred can do it in 3 hours, and John can do it in 6 hours. How long will it take them working together?
Understand that there is one job.
Fred works at a rate of 1 job 2 job
——— call this ——— to enable you to add it to John's rate
3 hr 6 hr
John works at a rate of 1 job
———
6 hr
Add them together and you get 3 job 1 job
——— which is ——— together they do the job in 2 hours
6 hr 2 hr
This kind of problem was so hard for me when I was in school. It took me forever to grasp how to do it.
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