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Math Help - urgent help in math grade 10 linear equations

  1. #1
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    urgent help in math grade 10 linear equations

    hey guys i really need help with these two questions
    im studying for my math exam right now which im taking tomorrow
    plz some1 help!

    a traffic helicopter finds that with a tailwind her 120 km trip away from the airport takes 30 min. on her return trip to the airport, into the wind, she finds that her trip is 10 min longer . What is the spped of the helicopter. what is the speed of the wind?

    second question

    rani is comparing the monthly costs fromo two internet service providers. nextaxes charges a flat monthly fee of $10, plus $0.75 per hour spend on-line. Webz changes a flat monthly fee of $5 plus $1 per hour.
    a. determine when the monely costs are the same.
    b. rani plans to use the internet for a tleast 30h each month. which provide should she choose.
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  2. #2
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    1st question is simultaneous equations, 1st find the speed of the journey there where speed =distance/time
    then the speed of the journey back.

    Then do 2 equations as shown where helicopter speed is h and wind is w

    you have 2 equations

    h + w = speed of journey there
    h - w = speed of journey back

    adding the 2 equations would give 2h=speed of journey there = speed of journey back

    then do the same but subtract the 2nd equation from the 1st
    Last edited by checkthiskid; January 19th 2009 at 03:13 PM. Reason: typo
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  3. #3
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    Quote Originally Posted by xo-sherry View Post
    hey guys i really need help with these two questions
    im studying for my math exam right now which im taking tomorrow
    plz some1 help!

    a traffic helicopter finds that with a tailwind her 120 km trip away from the airport takes 30 min. on her return trip to the airport, into the wind, she finds that her trip is 10 min longer . What is the spped of the helicopter. what is the speed of the wind?

    second question

    rani is comparing the monthly costs fromo two internet service providers. nextaxes charges a flat monthly fee of $10, plus $0.75 per hour spend on-line. Webz changes a flat monthly fee of $5 plus $1 per hour.
    a. determine when the monely costs are the same.
    b. rani plans to use the internet for a tleast 30h each month. which provide should she choose.
    2nd question is easier
    make 2 equations where no of hours used per month = h and monthly fee=m

    for nettaxes we have m=10+0.75h
    for webz we have m=5+1h

    for the point when the cost we do equation 1 = equation 2

    10+0.75h=5+1h

    rearrange these to get all the h values on 1 side and the number son the other

    0.25h = 5

    the value u find for h is the number of hours used per month with the same cost



    for net taxes we have mo

    2nd part of this question simply

    substitute the h in your original 2 equations to find which is the cheapest
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  4. #4
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    this is what i tried doing but i still can't get the right answer can some1 check if im doing something wrong:

    so i figure out the speed by using this forumula
    s=d/t

    i got 4 for going there and 3 for going back

    then i used my 2 equations

    b+c=4
    b-c=3

    2b=7
    b=3.5

    then replace
    3.5 + c = 7
    c= 7- 3.5
    c=1.5

    but in my answer book it shows that the answer is the speed of the helicopter is 210km/h and the wind is 30 km/h
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  5. #5
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    Quote Originally Posted by xo-sherry View Post
    this is what i tried doing but i still can't get the right answer can some1 check if im doing something wrong:

    so i figure out the speed by using this forumula
    s=d/t

    i got 4 for going there and 3 for going back

    then i used my 2 equations

    b+c=4
    b-c=3

    2b=7
    b=3.5

    then replace
    3.5 + c = 7
    c= 7- 3.5
    c=1.5

    but in my answer book it shows that the answer is the speed of the helicopter is 210km/h and the wind is 30 km/h
    an error i originally made myself

    the speed you have is in km per minutes since the original time given was in minutes multiply your answer by 60 to get km/h
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  6. #6
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    Quote Originally Posted by checkthiskid View Post
    an error i originally made myself

    the speed you have is in km per minutes since the original time given was in minutes multiply your answer by 60 to get km/h
    lol heyy!
    nah it's okay!
    but yah i figured it out! thankss soo sooo much!!!
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  7. #7
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    Quote Originally Posted by xo-sherry View Post
    this is what i tried doing but i still can't get the right answer can some1 check if im doing something wrong:

    so i figure out the speed by using this forumula
    s=d/t

    i got 4 for going there and 3 for going back

    then i used my 2 equations

    b+c=4
    b-c=3

    2b=7
    b=3.5

    then replace
    3.5 + c = 7
    c= 7- 3.5
    c=1.5

    but in my answer book it shows that the answer is the speed of the helicopter is 210km/h and the wind is 30 km/h
    u subbed b into the equation incorrectly
    it should have been

    3.5+c=4
    c=0.5

    (0.5*60=30 theres your wind speed)
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