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Math Help - Please help me with this question!

  1. #1
    Member princess_anna57's Avatar
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    Wink Please help me with this question!

    Please help!

    A service station has 2 kinds of oil, one selling for $1.27/litre and the other for $1.18/litre. How many litres of each must be used to make 90 litres of a mixture that can be sold for $1.24/litre?
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by princess_anna57 View Post
    Please help!

    A service station has 2 kinds of oil, one selling for $1.27/litre and the other for $1.18/litre. How many litres of each must be used to make 90 litres of a mixture that can be sold for $1.24/litre?
    Let x be the number of litres of the 1.27 oil, then there are 90-x litres of
    the other. The price of the mixture will be:

    (1.27*x+1.18*(90-x))/90 dollars per litre.

    You will need to find x such that the price of the mixture will be 1.24.

    RonL
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  3. #3
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    Quote Originally Posted by princess_anna57 View Post
    Please help!

    A service station has 2 kinds of oil, one selling for $1.27/litre and the other for $1.18/litre. How many litres of each must be used to make 90 litres of a mixture that can be sold for $1.24/litre?
    Hello,

    let x be the amount of oil which is sold for $1.27
    then (90-x) is the amount of oil which is sold for $1.18.

    Now you can set up the equation:

    x \cdot 1.27 - (90-x) \cdot 1.18 = 90 \cdot 1.24 . Expand the bracket and collect like terms :

    x \cdot 1.27 - x \cdot 1.18 = 90 \cdot 1.24 - 90 \cdot 1.18

    x \cdot 0.09 = 5.4 . Divide both sides of the equation by 0.09 and you'll get:

    x = 60

    That means: Take 60 ltrs of the $1.27-oil and 30 ltrs of the $1.18-oil to get the mixture which you can sell for $1.24
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