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Math Help - Equation Help

  1. #1
    Newbie
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    Sep 2008
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    Exclamation Equation Help

    Hey everyone,
    I was hoping someone who is a little better at math might be able to help me out. Not necessarily give me answers, but lead me in the right direction. Please help if you can!

    1)Mary Chai invested two sums of money, the first at 10% and the second at 12%. The ratio of the amounts invested was 8:5. What was the amount of each investment if the interest on the first investment was $200 per year more than the interest on the second investment?

    2)Two cars started at the same time from towns that are 615 km apart and met in 5 hours. What was the average speed of each car if one car went 15 km/hr faster than the other?

    Again, I don't need the answer, just if someone could show or explain to me how to set it up, it would be greatly appreciated. If you could just explain what the let statements are and how to set up the equation, that would be great!
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  2. #2
    MHF Contributor
    Joined
    Apr 2005
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    Quote Originally Posted by amkroese View Post
    Hey everyone,
    I was hoping someone who is a little better at math might be able to help me out. Not necessarily give me answers, but lead me in the right direction. Please help if you can!

    1)Mary Chai invested two sums of money, the first at 10% and the second at 12%. The ratio of the amounts invested was 8:5. What was the amount of each investment if the interest on the first investment was $200 per year more than the interest on the second investment?

    2)Two cars started at the same time from towns that are 615 km apart and met in 5 hours. What was the average speed of each car if one car went 15 km/hr faster than the other?

    Again, I don't need the answer, just if someone could show or explain to me how to set it up, it would be greatly appreciated. If you could just explain what the let statements are and how to set up the equation, that would be great!
    1.)
    A at 10%; A at 12%
    A/B = 8/5

    I = PRT
    In 1 year,
    I(A) = A*10%
    I(B) = B*12%
    I(A) = I(B) +200

    You should get A = $8000 and B = $5000

    -------------------
    2.)

    didstance = rate * time

    r2 = r1 +15

    (r1)*5 +(r2)*5 = 615

    You should get r1 = 54 km/hr and r2 = 69 km/hr.
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