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Math Help - Algebra problem involving standard notation & %.

  1. #1
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    Algebra problem involving standard notation & %.

    Please help me solve these three problems:

    The human body can produce 2.5 million blood cells per second. If a person donates 500mL of blood, how long will it take to replace the red blood cells if a litre of blood contains 5 * (10^12) red blood cells?


    The Sun is approximately 1.5 * (10^8) km from Earth and a comet is approximately 3 * (10^6) km from Earth. How many times further from Earth than the comet is the Sun?


    A music store sells three types of CDs: classical, blues and heavy metal. In one week the sold a total of 420 CDs. They sold 10% more classical than blues whiles sales of heavy metal constituted 50% more than the combined sales of classical and blues CDs. How many of each type of CD did they sell?


    Thanks in advance!
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    Quote Originally Posted by delicate_tears View Post
    Please help me solve these three problems

    A music store sells three types of CDs: classical, blues and heavy metal. In one week the sold a total of 420 CDs. They sold 10% more classical than blues whiles sales of heavy metal constituted 50% more than the combined sales of classical and blues CDs. How many of each type of CD did they sell
    Thanks in advance!

    [I]
    let x be classical
    Blues: 0.10x+x
    Classical and blues:0.10+2x
    heavy metals: 0.5(0.10+2x)+(0.10+2x)= 3.15x


    x+0.10x+x+0.5(0.10+2x)+(0.10+2x)= 420

    2.1x+3.15x=420

    5.25x=420

    x=80

    classical= 80
    Blues= 0.10(80)+80 =88
    heavy metals= 3.15(80)=252

    80+88+252=420



    Last edited by princess_21; January 24th 2009 at 03:27 AM.
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  3. #3
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    Quote Originally Posted by delicate_tears View Post
    Please help me solve these three problems:

    The human body can produce 2.5 million blood cells per second. If a person donates 500mL of blood, how long will it take to replace the red blood cells if a litre of blood contains 5 * (10^12) red blood cells?
    \frac{5*10^{12}}{2}=2.5*10^{12}

    \frac{2.5*10^{12}}{2500000}=10000seconds

     10000 s * \frac{1min}{60s}

    166.66 hrs
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  4. #4
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    Quote Originally Posted by delicate_tears View Post
    [snip]
    The Sun is approximately 1.5 * (10^8) km from Earth and a comet is approximately 3 * (10^6) km from Earth. How many times further from Earth than the comet is the Sun?

    [snip]
    \frac{1.5 \cdot 10^8}{3 \cdot 10^6} and the simplification should be straightforward.
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