Dave can ride the merry-go-round for 10 minutes and Chuck can ride 5 times longer than Dave so he can ride for 10*5 = <<10*5=50>>50 minutes
Erica can stay on 30% longer than Chuck who can ride for 50 minutes so that's an extra .30*50 = <<30*.01*50=15>>15 minutes
Chuck can ride for 50 minutes and Erica can ride an extra 15 minutes for a total of 50+15 = <<50+15=65>>65 minutes
#### 65