Mrs. M drove 10 minutes at 60 miles per hour, then 20 minutes at 30 miles per hour. For the rest of the hour, she drove at a rate that put her 48 miles from her starting point. What was the rate?

96 miles per hour

Explanation:

10min=1/6h           (1/6)*60= 10 miles

20min=2/6h         (2/6)*30= 10 miles

the rest of the hour=1h - (1/6h+2/6h)=1/2h

in 1/2h she travels 48 miles then in 1 hour she travels (48*2)=96 miles per hour