WALT: relate tables, graphs, and equations to linear and simple quadratic relationships found in number and spatial patterns.

Assessment Task: A car rental business has two rental schemes, red and blue for rentals up to ten days. These schemes are advertised in their brochures with this graph.

Use the following information to work out how many days of rental would carry the same total cost on either the blue or the red scheme (show your working).
The area under the graph gives the total cost of renting.
The schemes each follow a linear pattern, cutting the vertical axis at 120 and 170.
Both blue and red schemes cost $110 on the 4th day of rental.

Day	Cost per day
0	170
1	155
2	140
3	125
4	110
5	95
6	80
7	65
8	50

Day	Cost per day
0	120
1	117.5
2	115
3	112.5
4	110
5	107.5
6	105
7	102.5
8	100

The cost was the same on the forth day.