The number of songs in a playlist is 300. If John has 20 such playlists, and each song is 10 hours long, how many hours will the 20 playlists last in total?
Since each playlist has 300 songs, the total number of songs in the 20 playlists is 20*300= <<20*300=6000>>6000.
If each song is 10 hours long, the 6000 songs in the 20 playlists last a total of 6000*10 = <<6000*10=60000>>60000 hours
#### 60000