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Math Help - phone bill

  1. #1
    Senior Member sfspitfire23's Avatar
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    phone bill

    Given that a phone call is charged x cents in the first minute and y cents from the second min onwards. How many minutes did a person speak, if his bill is $4.94?
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  2. #2
    MHF Contributor undefined's Avatar
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    Quote Originally Posted by sfspitfire23 View Post
    Given that a phone call is charged x cents in the first minute and y cents from the second min onwards. How many minutes did a person speak, if his bill is $4.94?
    Not enough information. He could be charged 494 cents for the first minute, then he spoke 1 minute; or he could be charged 493 cents for the first minute and 1 cent for the second minute, in which case he spoke two minutes, and we can find examples all the way until 495 minutes, assuming x and y are non-negative integers.

    Actually, if x = 494 and y = 0 then he could have spoken any number of minutes > 0.
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  3. #3
    Senior Member eumyang's Avatar
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    Maybe this is an exercise in literal equations? If we say that t = time spoke in minutes, the equation could be written as

    x + y(t - 1) = 494
    (using cents as the unit)

    You can still solve for t like this:
    \begin{aligned}<br />
x + y(t - 1) &= 494 \\<br />
y(t - 1) &= 494 - x \\<br />
t - 1 &= \dfrac{494 - x}{y} \\<br />
t &= \dfrac{494 - x}{y} + 1<br />
\end{aligned}
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