Jack and Serena can write a lab report together in 6 hours. If all people work at the same rate, how many hours would it take to write a lab report if Kay joins Jack and Serena?
If two people can do a job in 6 hours, that means it would take 1 person 6 * 2= 12 hours to do the job. If it takes 12 hours to do the job, then with 3 people it will take 12 / 3= 4 hours to do the job.
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