On the last night that roller skate rink was open, 40 people showed up to roller skate one last time.  When all 40 people skated at one time, how many wheels were on the floor?
40 people were roller skating and they all had 2 feet which means there were 40*2 = <<40*2=80>>80 feet
Each foot needs a roller skate and each roller skate has 4 wheels so 80*4 = <<80*4=320>>320 wheels when everyone skated
#### 320