Mickey runs around the block twice because half of 4 is <<4/2=2>>2.
Mickey runs 400 meters in total because 2 times 200 equals <<2*200=400>>400.
Johnny runs 800 meters because 4 times 200 equals <<4*200=800>>800.
In total, they run 1200 meters because 400 plus 800 equals 1200.
On average, they run 600 meters because 1200 divided by 2 equals <<1200/2=600>>600
#### 600