LInear graph Question

Question

An airline charges $300 for a fl ight of 2000 km and $700 for a flight of 4000 km.
(a) Plot these points on graph paper with distance on the horizontal axis and cost on
the vertical axis.
(b) Assuming a linear model estimate
(i) the cost of a flight of 3200 km
(ii) the distance travelled on a flight costing $400.

Answer 1

Hopefully you know how to plot the points. 

 

To find the slope:

 

(700 - 300)/(4000 - 2000) = 400/2000 = 1/5

 

To find b, the y-intercept, use either point.

 

300 = (1/5)2000 + b

300 = 400 + b

b = -100

 

c = (1/5)3200 - 100

c = 640 - 100

c = $540

 

400 = (1/5)m - 100

500 = (1/5)m

m = 2500 miles

 

If all that algebra was too much, perhsps you were to draw a line connecting your two points and estimating each from your graph.