# 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

• 最愛解答

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~
• 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
• let A =cost of surfing per hour

B= fixed cost

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

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

(from 1) =&gt; B=173-35A ------(3)

substitute (3) into (2) =&gt;48A+173-35A=212

13A=39

A=3

B=68