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:
| Home team | Home team score | Away team | Away team score | Venue | Crowd | Date |
| --- | --- | --- | --- | --- | --- | --- |
| Geelong | 15.13 (103) | Richmond | 9.11 (65) | Kardinia Park | 19565.0 | 30 April 1955 |
| Essendon | 11.14 (80) | North Melbourne | 9.15 (69) | Windy Hill | 21000.0 | 30 April 1955 |
| Collingwood | 16.20 (116) | St Kilda | 8.11 (59) | Victoria Park | 18095.0 | 30 April 1955 |
| Carlton | 17.4 (106) | Fitzroy | 6.13 (49) | Princes Park | 23435.0 | 30 April 1955 |
| South Melbourne | 7.14 (56) | Hawthorn | 15.8 (98) | Lake Oval | 18000.0 | 30 April 1955 |
| Melbourne | 6.22 (58) | Footscray | 6.10 (46) | MCG | 49280.0 | 30 April 1955 |
Question:
When North Melbourne played as the away team, what was the crowd numbers?
Answer:
21000.0