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Thread: Tough Word Problem.

  1. #1
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    Tough Word Problem.

    A particular disc can be made to rotate at 2 different speeds. If it were made to rotate slower by 135 revolutions per hour, it would require an additional 2.7-hour to make 315 revolutions. Find the higher speed at which it can operate.
    Last edited by mr fantastic; Oct 25th 2010 at 11:41 AM. Reason: Edited title.
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    Quote Originally Posted by Arka View Post
    A particular disc can be made to rotate at 2 different speeds. If it were made to rotate slower by 135 revolutions per hour, it would require an additional 2.7-hour to make 315 revolutions. Find the higher speed at which it can operate.
    let $\displaystyle \omega$ be the higher speed of rotation in rev/hr

    $\displaystyle t$ = time in hrs to rotate 315 rev at the higher speed

    $\displaystyle \omega t = 315$

    $\displaystyle (\omega - 135)(t+2.7) = 315$

    solve the system of equations for $\displaystyle \omega$ ... I'd start by using the first equation and solving for $\displaystyle t$ in terms of $\displaystyle \omega$, then substitute for $\displaystyle t$ in the second equation.
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