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Math Help - Solving unknowns

  1. #1
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    Solving unknowns

    1. If x^2 - y^2=10 and x+y=5, what is the value of x-y?

    I've tried to figure it out with substitution/simultaneous equations but I keep getting wrong answers..

    The actual answer is 2

    2. The average (arithmetic mean) of the test scores of a class of p students is 70 and the average of the test scores of a class of n students is 92. When the scores of bloth classes are combined, the avg. score is 86. What is the value of p/n?
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  2. #2
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    Hint for question 1 :

    x^2 - y^2 = (x+y)(x-y)

    You should be able to solve and get the correct answer
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  3. #3
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    Oct 2008
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    Singapore
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    Hint for question 2 :

    (Total score of class p students + Total score of class n students) / ( Total number of students in both class ) = 86
    (70p + 92n) / (n + p) = 86

    Manipulate the above equation to help you get the answer for p/n . Hope it helps.
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