Answer :
Final answer:
To find how long it would take Ann and Bob to complete a job together, calculate their combined work rate and determine the time needed to finish one job.
Explanation:
To calculate how long it would take Ann and Bob to complete a job together, we need to add their individual rates of work.
Ann can complete the job in 30 minutes, which is 1/2 hour, so her work rate is 1 job per 0.5 hours. Bob can complete the job in 70 minutes, which is 1 hour and 10 minutes, so his work rate is 1 job per 1.167 hours.
Together, their work rate is 1/0.5 + 1/1.167 = 3.667 jobs per hour. To calculate how many minutes it would take to complete one job together, we take the reciprocal of this rate, which is about 0.273 hours or 16.4 minutes.
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