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I am working on Measurements and it is one of the most difficult things for me to do. Topics include the SI measurement, Imperial Measurement, and Converting between SI and Imperial Systems.

I would like to do some review on this and would like to know a easier way to all problems.

Montgomery ran 100m in 9.78s. What was the runner's speed in kilometres per hour?

How do I do this? Do I convert metres to kilometres first? How do I convert seconds to hours? I just don't get it . Can someone please provide me with clarification.

  • MATH -

    maybe this will make sense to you .....

    100 m = .1 km
    and 1 sec = 1/(60x60) or 1/3600 hour

    so 100 m/9.78 sec
    = .1 km/(9.78 x 1/3600) hr
    = 36.8 km/hr

    or look at it this way ...
    there are 3600 seconds in 1 hour.
    so by dividing 3600 by 9.78 we would get 368 legs of 100 m, but 10 of those 100 stretches make 1 km, so divide 368 by 10 to find the number of km
    or 36.8 km/hr

    I would simply form a ratio using the same units the same units
    .1 km/9.78 sec = xkm/3600 sec
    cross multiply
    9.78x = .1(3600)
    x = 360/9.78
    x = 36.8

    so x = 36.8 km/3600 sec
    = 36.8 km/hr

  • MATH -

    That does make a lot of sense, thank you very much Reiny!

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