You pay $20 for 200 min math class, and pay $60 for 400 min.

Question

a) graph to show the cost per days.

b)write down the equation of your graph

c) how many minutes can I have with $40?

d) what is the cost for 600 minutes ?

Answer 1

(200, 20), (400, 60)

slope= 40/200= 1/5= (y-20)/(x-200)

5y-100= x-200

y= f(x)= x/5 -20 y intercept is (0, -20)

x intercept is (100, 0) first 100 minutes are free

plot the 2 intercepts and draw a line through them but really only use the line in quadrant 1

40=x/5-20

x/5=60

x= 300 minutes for $40 (300, 40)

y= 600/5 -20= 120-20 = 100 $100 buys 600 minutes