Question

The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May her driving cost was $380 for 300 mi and in June her cost was $500 for 900 mi. Assume that there is a linear relationship between the monthly cost C of driving a car and the distance driven d.
(a) Find a linear equation that relates C and d.


(b) Use part (a) to predict the cost of driving 1600 mi per month.

Answer 1

linear relationship
therefore eqn of line is y = mx + b
y = cost = C
x = miles = d

find m
find b

m = gradient = y2-y1 / x2 - x1

Answer 2

m= 5

Answer 3

cool, so b = y intercept
so use m = 5 to find b

Answer 4

use example y = 380, d = 300

Answer 5

what?

Answer 6

y = mx + b
$380 = 5 * 300miles + b
380 = 1500 + b
b = 380 / 1500 = 0.2533

Answer 7

so y=5(x)+0.2533

Answer 8

no, sorry, as m = 1/5 = (0.2)
lets try again with that and get b = ...?

Answer 9

380 / 60 = b = 6.333

Answer 10

how does m=1/5?

Answer 11

y2 - y1 / x2 -x1
= 500 - 380 / 900 - 300
= 120 / 600
= 1/5

Answer 12

as cost ( y ) or ( C ) is dependant on distance (x) or (d) whichever you prefer to call it

Answer 13

are u following ok with that? @hannahmarie620

Answer 14

yes

Answer 15

so c= 1/5(d)+6.33

Answer 16

perfect

Answer 17

now just plug in d as 1600 and ur set

Answer 18

its wrong

Answer 19

i agree

Answer 20

i got 326
it looks soooo wrong, im sorry

Answer 21

aw dammit
it's b = 380 MINUS 60, not divide by

Answer 22

so b = 320, sot 6.3

Answer 23

y = mx +b
C = 1/5 d + b
using $500 and 900 miles
500 = 1/5 (900) + b
b = 500 - 180 = 320

so d = 1600
C = md + b
C = 1/5 * 1600 + 320
C = 320 + 320 = $640

Answer 24

sorry for the screw up before
i'll go to bed now

Answer 25

thank you!

Answer 26

whats the equation

Answer 27

nvm