SOLUTION: Find out the average rate of (i) motion in the case of a person who rides the first mile at the rate of 10 miles an hour, the next mile at the rate of 8 miles per hour, and the thi

Algebra ->  Probability-and-statistics -> SOLUTION: Find out the average rate of (i) motion in the case of a person who rides the first mile at the rate of 10 miles an hour, the next mile at the rate of 8 miles per hour, and the thi      Log On


   

Question 1114525: Find out the average rate of (i) motion in the case of a person who rides the first mile at the rate of 10 miles an hour, the next mile at the rate of 8 miles per hour, and the third mile at the rate of 6 miles per hour; (ii) increase in population, which in the first decade has increased 20%, in the next 25% and in the third 44%.
Answer by ikleyn(52776) About Me  (Show Source):
You can put this solution on YOUR website!
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a)  The person rode 3 miles in total.


    For the 1-st mile he spent  1%2F10  of an hour.


    For the 2-nd mile he spent  1%2F8  of an hour.
    

    For the 3-rd mile he spent  1%2F6  of an hour.


    In all, he spent  1%2F10 + 1%2F8 + 1%2F6 = 12%2F120+%2B+15%2F120+%2B+20%2F120 = 47%2F120  of an hour.


    The average speed = distance%2Ftime = 3%2F%28%2847%2F120%29%29 = %283%2A120%29%2F47 = 7.66 miles per hour.

Solved.