Please read the following table in Markdown format and then answer the question according to the table. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| Rnd | Date | Race Name | Length | Track | Location | Type | Pole Position | Winning Driver |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| 1.0 | May 24, 1981 | Indianapolis 500-Mile Race | mi (km) | Indianapolis Motor Speedway | Speedway , Indiana | Paved oval | Bobby Unser | Bobby Unser |
| 2.0 | June 21, 1981 | Van Scoy Diamond Mines 500 | mi (km) | Pocono International Raceway | Long Pond , Pennsylvania | Paved oval | A. J. Foyt | A. J. Foyt |
| 3.0 | August 15, 1981 | Tony Bettenhausen 100 | mi (km) | Illinois State Fairgrounds | Springfield , Illinois | Dirt oval | Tom Bigelow | George Snider |
| 4.0 | August 30, 1981 | DuQuoin 100 | mi (km) | DuQuoin State Fairgrounds | Du Quoin , Illinois | Dirt oval | Bill Engelhart | Rich Vogler |
| 5.0 | September 12, 1981 | Hoosier Hundred | mi (km) | grounds Indiana State Fair | Indianapolis , Indiana | Dirt oval | Larry Rice | Larry Rice |
Question:
Which track was used on September 12, 1981? 
Answer:
grounds Indiana State Fair