question: 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?
answer: 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