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16 September, 09:41

a jogger ran 2 miles, decreased her speed by 1 mile per hour, and then ran another 3 miles. If her total jogging time was 11/14 hours, find her speed for each part of her run

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  1. 16 September, 10:33
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    7 mph, 6 mph

    Step-by-step explanation:

    Let's say x is her speed during the first 2 miles, and x-1 is her speed during the last 3 miles.

    The time it takes for her to run the first 2 miles is:

    t = 2 / x

    The time it takes for her to run the last 3 miles is:

    t = 3 / (x-1)

    The total time is 11/14 hours:

    11/14 = 2/x + 3 / (x-1)

    Multiply both sides by x (x-1).

    11/14 x (x-1) = 2 (x-1) + 3x

    11/14 (x²-x) = 2x - 2 + 3x

    11/14 (x²-x) = 5x - 2

    Multiply both sides by 14:

    11 (x²-x) = 70x - 28

    11x² - 11x = 70x - 28

    11x² - 81x + 28 = 0

    Factor:

    (11x - 4) (x - 7) = 0

    x = 4/11 or 7

    Since x must be greater than 1 (x-1 must be positive), that means x = 7 and x-1 = 6.

    Her speed during the first part was 7 mph, and her speed during the second part was 6 mph.
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