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Math Help - Substitution word problem

  1. #1
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    Substitution word problem

    I realise I posted this in the wrong forum sorry
    this is grade 10

    the problem is:
    a silversmith has alloys that contain 40% silver and others that have 50% silver. A custom order requires 150g of 44% silver. How much of each alloy should be melted together to make the bracelet?

    so far i got:
    Let x represent the 40% alloy
    Let y represent the 50% alloy.

    x+y=150
    0.4x+0.5y=0.44

    I rearranged the first eqaution to be y=-x+150.
    Then subbed it into the second to be 0.4x+0.5(-x+150)=0.44
    but when I solved this, i got 745.6. Where did I go wrong?
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  2. #2
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by questions4u View Post
    I realise I posted this in the wrong forum sorry
    this is grade 10

    the problem is:
    a silversmith has alloys that contain 40% silver and others that have 50% silver. A custom order requires 150g of 44% silver. How much of each alloy should be melted together to make the bracelet?

    so far i got:
    Let x represent the 40% alloy
    Let y represent the 50% alloy.

    x+y=150
    0.4x+0.5y=0.44

    I rearranged the first eqaution to be y=-x+150.
    Then subbed it into the second to be 0.4x+0.5(-x+150)=0.44
    but when I solved this, i got 745.6. Where did I go wrong?
    your second equation is wrong. it should be equated to 66 (which is 44% of 150g) not 0.44. you let x and y represent the grams of silver in the first equation and then the percentage of silver in the second. this inconsistency gave rise to your incorrect solution
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  3. #3
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    thank you
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