SOLUTION: An automobile is driven at 30 mph for 12 min, then at 40 mph for 20 min, and finally 50 mph for 8 min. (a) Determine the average speed over the interval. (b) How fast must the

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Question 1165400: An automobile is driven at 30 mph for 12 min, then at 40 mph for 20 min, and
finally 50 mph for 8 min.
(a) Determine the average speed over the interval.
(b) How fast must the automobile move in the last 8 min to obtain an average speed of 35
mph?
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
(a)

30%2A%2812%2F60%29%2B40%281%2F3%29%2B50%288%2F60%29=26-------------miles of the entire distance.

12%2B20%2B8=40-----------2%2F3hour------------time for the entire distance.

26%2F%282%2F3%29=3%2A26%2F2=39mph-----------average speed