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匿名 發問於 科學及數學數學 · 1 十年 前

Linear Equations in Two Unknowns

APPLICATIONS OF SIMULTANEOUS LINEAR EQUATIONS IN TWO UNKNOWS :

1)The customer of an internet company has to pay a fixed cost plus an extra amount calculated according to the web- surfing time .if a customer spends 35hours for web-surfing,the payment is $173.if he spends 48hours for web-surfing,the payment is$212.find the fixed cost and the amount for web-surfuing per hour.

3 個解答

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  • sunny
    Lv 5
    1 十年 前
    最佳解答

    1)The customer of an internet company has to pay a fixed cost plus an extra amount calculated according to the web- surfing time .if a customer spends 35 hours for web-surfing, the payment is $173.if he spends 48 hours for web-surfing, the payment is $212.Find the fixed cost and the amount for web-surfuing per hour.

    Let the fixed cost be $a, the amount for web-surfuing per hour be $b

    a + 35b = 173............(1)

    a + 48b = 212............(2)

    (2) - (1) :

    a + 48b - a - 35b = 212 - 173

    13b = 39

    b = 3 //

    Substitute b = 3 into (1)

    a + 35(3) = 173

    a + 105 = 173

    a = 68 //

    The fixed cost is $68, the amount for web-surfuing per hour is $3

    2007-02-05 17:45:53 補充:

    上述問題我用左 method of elimination~你亦可用method of substitution~a + 35b = 173............(1)a + 48b = 212............(2)From (1)a = 173 - 35b..............(3)Substitute (3) into (2)173 - 35b + 48b = 21213b = 39b = 3 //

    2007-02-05 17:46:04 補充:

    Substitute b = 3 into (1)a 35(3) = 173a 105 = 173a = 68 //The fixed cost is $68, the amount for web-surfuing per hour is $3

    資料來源: me~
  • 1 十年 前

    Let x be the fixed cost and y be the amount for web-surfing per hour

    x+35y=173......(1)

    x+48y=212......(2)

    (2)-(1),(x+48y)-(x+35y)=212-173

    x-x+48y-35y=39

    13y=39

    y=39/13

    y=3

    Sub y=3 into (1)

    x+35*3=173

    x+105=173

    x=173-105

    x=68

    資料來源: myself
  • 1 十年 前

    let A =cost of surfing per hour

    B= fixed cost

    35A+B =173 ------(1)

    48A+B =212 ------(2)

    (from 1) => B=173-35A ------(3)

    substitute (3) into (2) =>48A+173-35A=212

    13A=39

    A=3

    B=68

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