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Math Help - A troubling for me...

  1. #1
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    A troubling for me...

    Students in an elementary class decided to spend D dollars for a present for their favourite teacher, Mrs B, each contributing an equal amount. Because 15 students refused to contribute, each of those remaining agreed to contribute an additional, equal amount. What was the additional amount each had to contribute, in dollars?

    =)
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by nathan02079 View Post
    Students in an elementary class decided to spend D dollars for a present for their favourite teacher, Mrs B, each contributing an equal amount. Because 15 students refused to contribute, each of those remaining agreed to contribute an additional, equal amount. What was the additional amount each had to contribute, in dollars?

    =)
    let x be the total number of students in the class. then each must give \frac Dx dollars

    but since only (x - 15) will give, they must give \frac D{x - 15} dollars.

    thus, the additional amount the giving students must give is  \left( \frac D{x - 15} - \frac Dx \right) dollars. call this amount E

    thus, the amount extra each giving student must give is \left( \frac E{x - 15}\right) dollars

    now substitute the equation for E and simplify
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