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anonymous

  • 5 years ago

Suppose that both 75% brass and 90% brass are available. How many pounds of each must be mixed to get 150 pounds of 87% brass? My book answers were x=30 pounds of 75% brass and y= 120 pounds of 90% brass. I wanted to know how to get that answer-- what is the equation is it x + y= 150 and ???????

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  1. anonymous
    • 5 years ago
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    30*0.75+120*0.9=150*0.87

  2. anonymous
    • 5 years ago
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    so it is x*0.75+y*0.9=150*0.87

  3. anonymous
    • 5 years ago
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    plus x+y=150

  4. anonymous
    • 5 years ago
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    and if you solve these two equations than you get the result

  5. anonymous
    • 5 years ago
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    I will key in with my scientific calculator. sounds right wait.... thank you

  6. anonymous
    • 5 years ago
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    but the 30 and 120 is not given..... that is the answer at the back of my book

  7. anonymous
    • 5 years ago
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    yes that is what confused me :D

  8. anonymous
    • 5 years ago
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    hey he gave us a clue that brass is made of copper and zinc--- it means the other percentage to make a 100% is a zinc.

  9. anonymous
    • 5 years ago
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    but now it is clear. let x be the 75% one and y the 90% than we want to make 150 pounds so x+y=150 also we want to get 87% brass so x*0.75+y*0.9=150*0.87

  10. anonymous
    • 5 years ago
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    y=150-x from first equation you plug this into the second 0.75x +(150-x)*0.9=150*0.87

  11. anonymous
    • 5 years ago
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    this gives 4.5=0.15x so x=30 y=(150-x)=120

  12. anonymous
    • 5 years ago
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    I am using scientific calculator using the command matrix.... ok let me do that.

  13. anonymous
    • 5 years ago
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    calculators are bad... they do the work for you but you dont think

  14. anonymous
    • 5 years ago
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    hehehe! yah.... but we are allowed to use it though in math modeling... i hate math ill be glad to get out in this class... its the only math i will be taking in nursing. thank goodness

  15. anonymous
    • 5 years ago
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    :-)

  16. anonymous
    • 5 years ago
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    did you get the result by the way?

  17. anonymous
    • 5 years ago
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    not yet im still trying to figure out how to key in figures using matrix command.

  18. anonymous
    • 5 years ago
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    I did not use a calculator and had the answer 10 minutes ago :-)

  19. anonymous
    • 5 years ago
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    hahahaha!

  20. anonymous
    • 5 years ago
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    thanks for your time andras--- I got the answer solving manually using your equation. But i donno how to key in the scientific calculator though--thanks for your effort. love this site.

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