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Math Help - elimination and substitution word problem

  1. #1
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    elimination and substitution word problem

    Hi guys , i am in grade 10 gifted math and am doing a series of word problems that involve elimination and substitution. I am good at math , but am still a bit ESL , so am having trouble decoding the first 2 equations that i am supposed to have.

    The question is : A car averages 8.5L/100km in city driving and 6.3L/100km on the highway. In 720km of driving , it used 55.7L of fuel.
    a)How far was the car driven in the city?
    b)How much fuel did it use in city driving?

    From what i read i figured that i would let the distance driven in the city be c km , and the distance driven in the highway be h km

    The first equation in my opinion should be
    c+h=720

    I am unsure however on what the second equation should be.

    I tried 8.5c+6.3H=720(55.7)

    and my end-result of c , was over 1900. Obviously i made a mistake there x(.
    i was thinking of doing it as 8.5c/100+ 6.3h/100= 720(55.7)/100 but this would simply give me the same wrong answer.

    Any help would be much appreciated
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  2. #2
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    I apologize for not following the proper forum edicate but this is an urgent matter. Please help
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  3. #3
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    Quote Originally Posted by mathdumby View Post
    Hi guys , i am in grade 10 gifted math and am doing a series of word problems that involve elimination and substitution. I am good at math , but am still a bit ESL , so am having trouble decoding the first 2 equations that i am supposed to have.

    The question is : A car averages 8.5L/100km in city driving and 6.3L/100km on the highway. In 720km of driving , it used 55.7L of fuel.
    a)How far was the car driven in the city?
    b)How much fuel did it use in city driving?

    From what i read i figured that i would let the distance driven in the city be c km , and the distance driven in the highway be h km

    The first equation in my opinion should be
    c+h=720

    I am unsure however on what the second equation should be.

    8.5 L/100 kg = .085 L/kg
    6.3 L/100 kg = .063 L/kg

    I tried 8.5c+6.3H=720(55.7) ===>.085c + .063h = 55.7

    and my end-result of c , was over 1900. Obviously i made a mistake there x(.
    i was thinking of doing it as 8.5c/100+ 6.3h/100= 720(55.7)/100 but this would simply give me the same wrong answer.

    Any help would be much appreciated
    *
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  4. #4
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    thank you ! Much appreciated friend
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