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Math Help - Hand of a Clock

  1. #1
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    Hand of a Clock

    Through how many radians does the minute hand of a clock turn in 24 minutes?
    (1) 0.2π (3) 0.67π
    (2) 0.4π (4) 0.8π


    MY WORK:

    24 minutes/60 minutes = 2/5 = 0.4pi or so I thought.

    The correct answer is 0.8pi.

    How can this be?

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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by magentarita View Post
    Through how many radians does the minute hand of a clock turn in 24 minutes?
    (1) 0.2π (3) 0.67π
    (2) 0.4π (4) 0.8π


    MY WORK:

    24 minutes/60 minutes = 2/5 = 0.4pi or so I thought.

    The correct answer is 0.8pi.

    How can this be?

    You're on the right track. What you did with the 24 min/ 60 min = 2/5 is good...but we have 2/5 of what? The whole circle. A circle has how many degrees [or radians, in this case] in it? Multiply 2/5 to that and see what you get.

    --Chris
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  3. #3
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    Do you???

    Quote Originally Posted by Chris L T521 View Post
    You're on the right track. What you did with the 24 min/ 60 min = 2/5 is good...but we have 2/5 of what? The whole circle. A circle has how many degrees [or radians, in this case] in it? Multiply 2/5 to that and see what you get.

    --Chris
    Do you mean multiply 2/5 times 360 degress or 2pi?

    I multiplied 2/5 by 360 degress and got 144.

    What did I do wrong?

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  4. #4
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by magentarita View Post
    Do you mean multiply 2/5 times 360 degress or 2pi?

    I multiplied 2/5 by 360 degress and got 144.

    What did I do wrong?
    In this case, you would multiply by 2\pi, since we are dealing with choices of angles in radians.

    --Chris
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