Question

An international calling plan charges a rate per minute plus a flat fee. A 10-minute call to France cost $3.19. A 15-minute call to France costs $4.29. Write and solve a linear equation to find the cost of a 12-minute call to France

Answer 1

$3.63

Explanation:

A 10-minute call to France cost $3.19.

`(x_1,y_1)=(10,3.19)`

A 15-minute call to France costs $4.29.

`(x_2,y_2)=(15,4.29)`

Now we will use two point slope form

`y-y_1=(y_2-y_1)/(x_2-x_1)(x-x_1)`

Substitute the values :

`y-3.19=(4.29-3.19)/(15-10)(x-10)`

`y-3.19=0.22(x-10)`

`y-3.19=0.22x-2.2`

`y=0.22x-2.2+3.19`

`y=0.22x+0.99`

y is the cost and x is the number of minutes

Now we are suppose to find cost of a 12-minute call to France

Substitute x = 12

`y=0.22(12)+0.99`

`y=3.63`

Hence the cost of a 12-minute call to France is $3.63