A gardener monitors the volume of water in a storage tank over 15 days of irrigation.
| Time (days) | Water (gallons) |
|---|---|
| 0 | 90 |
| 3 | 75 |
| 6 | 60 |
| 9 | 45 |
| 12 | 30 |
| 15 | 15 |
A line graph showing the relationship between time (days) on the x-axis and water volume (gallons) on the y-axis. The x-axis ranges from 0 to 20 with major grid lines every 5 units and minor grid lines every 1 unit. The y-axis ranges from 0 to 100 with major grid lines every 10 units. A straight line starts at (0,90)(0, 90)(0,90) and ends at (15,15)(15, 15)(15,15).
How much water was in the tank at the start of the 15 days?
How many more days can the tank supply water before it is empty?
What assumption have you made to calculate your answer to (b)?
