Both Polly and Peter played 30 / 2 =<<30/2=15>>15 moves each one
With an average of 28 seconds per move, Polly's moves lasted a total of 15 * 28 = <<15*28=420>>420 seconds.
With an average of 40 seconds per move, Peter's moves lasted a total of 15*40=<<15*40=600>>600 seconds.
In total, the match lasted 420 + 600 = <<420+600=1020>>1020 seconds.
In minutes, the match lasted 1020 / 60 = <<1020/60=17>>17 minutes
#### 17