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Math Help - Converting units - arithmetic and the calculator.

  1. #1
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    Converting units - arithmetic and the calculator.

    1) The speed of light is 3 X 10^8 m/s. Express this speed in miles/hour . ( 1 mile = 1609 m)

    my solving

    3X10^8X3600/1609 = 67122 ( why this is wrong answer no as my book )

    Itry by calculator I got 67122

    2 ) Calculate the diameter of a 2.0 cm length of tungsten filament in a small lighbulb if its resistance is 0.050 ohms

    I try to solve it
    2 cm = 200 m
    R= 0.050


    r = root P X l over Pi X R
    5.6 X 10^-8 X 2 X 10 ^ -2 over Pi X 0.05 = 4.220X10^-6

    dimetr = 2r
    = 2 ( 4.220X10^-6 ) 8.444016 X^-6
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  2. #2
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    Quote Originally Posted by r-soy View Post
    1) The speed of light is 3 X 10^8 m/s. Express this speed in miles/hour . ( 1 mile = 1609 m)

    my solving

    3X10^8X3600/1609 = 67122 ( why this is wrong answer no as my book )

    Itry by calculator I got 67122 Mr F says: Read the calculator display properly. The answer has more digits. The answer is 67122XXXX (the X's are for you to fill in).

    [snip]
    ..
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