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Math Help - 2 questions

  1. #1
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    Joined
    Feb 2008
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    7

    2 questions

    1 i have no clue how to do.. other somehwat...

    first one...

    2 student loans totalin 10,000.. he borrwed the max allowed at 7% simple interest and the remainder at 8.25% simple interest. After 1 year he owed 725 in interest.. how much did he borrow @ each interest rate

    first i did 10,000 x .07 = 700
    then 10,000 x .0825 = 825... but i dont know what to do, i dont think i did that step right


    second problem

    owned of video store sells 96 blank tapes per week if he charges 6 per tape. for every .50 he increases the price, he sells 4 fewer tapes per week.

    i have to write equations for price / # of tapes / revenue

    so woulnd't price = 6 + .5x
    tape = 96 - 4x
    revenue = (6 + .5x)(96 - 4x)

    how mcuh should he charge for a tape in order to make a revunue of 630 per week from the tapes


    any help is appreciated or point me in the right direction... thank you again!
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  2. #2
    Member
    Joined
    Dec 2007
    Posts
    131
    Quote Originally Posted by Ilovemath123 View Post
    1 i have no clue how to do.. other somehwat...

    first one...

    2 student loans totalin 10,000.. he borrwed the max allowed at 7% simple interest and the remainder at 8.25% simple interest. After 1 year he owed 725 in interest.. how much did he borrow @ each interest rate

    first i did 10,000 x .07 = 700
    then 10,000 x .0825 = 825... but i dont know what to do, i dont think i did that step right
    you have two equations here, where x is the "max" allowed and y is the "remainder"
    x+y = 10,000
    .07x+.0825y = 725

    solve top for x and then plug into the second:
    x = 10,000-y
    .07(10,000-y)+.0825y = 725 ==> .0125y+700=725 ==> y=2,000

    so then x+2000=10,000 ==> x=8,000



    Quote Originally Posted by Ilovemath123 View Post
    second problem

    owned of video store sells 96 blank tapes per week if he charges 6 per tape. for every .50 he increases the price, he sells 4 fewer tapes per week.

    i have to write equations for price / # of tapes / revenue

    so woulnd't price = 6 + .5x
    tape = 96 - 4x
    revenue = (6 + .5x)(96 - 4x)

    how mcuh should he charge for a tape in order to make a revunue of 630 per week from the tapes


    any help is appreciated or point me in the right direction... thank you again!
    your equations here seem right to me. now all you would do is solve for x in the equation 630 = (6 + .5x)(96 - 4x). i got x = 3 or x = 9. so he could charge either $7.50 or $10.50 to make $630 per week. the question doesnt say if the price or the tapes sold should be minimized or maximized, so either answer is right.
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