If Lou runs 3 miles during his workout on a track that is 1/4 miles long, then he circles the track 3/(1/4)=12 times.
If Rosie runs twice as fast as Lou, then over the same time period, she runs 3*2=<<3*2=6>>6 miles.
If Rosie runs 6 miles on the 1/4 mile track, then she circles the track 6/(1/4)=<<6/(1/4)=24>>24 times.
#### 24