What was the average amount of time each of the last 30 patients spent in the consulting room?

Question

In a doctors' surgery the first 15 patients were only in the consulting room for an average of three minutes each.

After a further 30 people had seen their doctor, the average number of minutes spent in the consulting room increased to eight minutes per patient.

What was the average amount of time each of the last 30 patients spent in the consulting room?

Answer 1

10.5 minutes

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Time spent for first 15 patients -> 15*3=45 minutes
Overall time spent for 15+30 patients -> 45*8=360 minutes
Average time spent for last 30 patients -> (360-45)/30= 10.5 minutes