1/2 hour ------------------------ 1/9
1 hour ------------------------ 2/9
1.5 hours ----------------------- 3/9
2 hours 4/9
2,5 nours 5/9
3 hours --------------------------- 6/9
3.5 hours ----------------------- 7/9
4 hours -----------------------8/9
4.5 hours --------------------------9/9 the entire battery
He must play for 4.5 hours to use the entire battery.