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    hey all, im bad at maths, can some one help me with this:

    A person travels 121 miles from the town of Newville to the city of Ewee at an average speed of 75 mph and then returns home at a more leisurely 58 mph.
    What was the average speed, correct to two decimal places, over the total distance covered?

    The answer is = 65.41353.. = 65.41, correct to two decimal places.

    Can some one pleeeeeease explain to me why that is the answer?

    thanks!!
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    Avarage speed = total distance / total time.

    So you need to calculate the time to get there and then time to get back to get total time. Total distance is just 121*2. Then plug these numbers into the formula.
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    (Original post by ttoby)
    Avarage speed = total distance / total time.

    So you need to calculate the time to get there and then time to get back to get total time. Total distance is just 121*2. Then plug these numbers into the formula.
    So are you saying it is 121/75 + 121/58 ?
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    (Original post by T.I.)
    So are you saying it is 121/75 + 121/58 ?
    That will give you the total time. You can calculate that and plug that number into the formula:

    Avarage speed = total distance / total time.
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    (Original post by ttoby)
    That will give you the total time. You can calculate that and plug that number into the formula:

    Avarage speed = total distance / total time.

    So it is (121/75) + (121/58) = (1.613333333 + 2.086206897) = 3.69954023

    121*2 = 242

    242/ 3.69954023 = 65.41353383 = 65.41


    Is that right buddy?
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    Evidently, as you posted the answer in your OP.
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    (Original post by tehforum)
    Evidently, as you posted the answer in your OP.
    I was just checking the workings, as i did that the first time around and got it wrong. grrrrrr.

    Do you know much about standard deviation?

    I have been asked the question:

    Find out the estimated standard deviation, using the n – 1 divisor, of the data.

    What would i have to do?
 
 
 
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