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Math Help - stamps problem

  1. #1
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    stamps problem

    hello

    we bought 100 stamps with total cost of 100 dollars
    the stamps are priced at 5, 3, and 0.5 dollars

    how many stamps of each price do we bought?

    can you solve it with equations and with logical/practical calculations?

    thanks
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  2. #2
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    e^(i*pi)'s Avatar
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    Quote Originally Posted by mathos View Post
    hello

    we bought 100 stamps with total cost of 100 dollars
    the stamps are priced at 5, 3, and 0.5 dollars

    how many stamps of each price do we bought?

    can you solve it with equations and with logical/practical calculations?

    thanks
    $5 stamps = a
    $3 stamps = b
    $0.50 stamps = c

    5a+3b+0.5c = 100
    a+b+c = 100

    Not sure where to go from there
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  3. #3
    Super Member Quacky's Avatar
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    Windsor, South-East England
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    $5 stamps = a
    $3 stamps = b
    $0.50 stamps = c

    (1)
    (2)
    (2) divided by 2:
    (3)  \frac {a}{2} + \frac {b}{2}+0.5c=50
    Hence,
     0.5c= 50-\frac {a}{2}-\frac {b}{2}
    Substituting this into equation (1) will give:
     5a + 3b + 50-\frac {a}{2}-\frac {b}{2}=100
    Which will eliminate c from one equation...I don't think that it can be done for another, which would then have allowed you to solve simultaneously because you only have 2 equations but 3 unknowns.
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