If a car travels 30.0 mi. north for 30.0 min., 50.0 mi. east for 1.00 hour, and 30.0 mi. south for 30.0 min., what is the average speed of the car over the total trip? 55 mph 55.0 mph 60.0 mph 60. mph

Note that Speed = Distance/Time.

1st trip:
Distance = 30 mi
Time = 30 min = 0.5 h
Speed = 30/0.5 = 60 mi/h

2nd trip:
Distance = 50 mi
Time = 1 hour
Speed = 50 mi/h

3rd trip:
Distance = 30 mi
Time = 30 min = 0.5 h
Speed = 30/0.5 = 60 mi/h

Average speed = (60 + 50 + 60)/3 = 56.7 mph
The closestanswer is 55 mph

55 mph

The answer which is not a detail carson used to describe the pool in the cave at low tide is b.  hundreds of periwinkles browse the branches and roots of the trees. 

It really doesn't matter for any of the questions that you've listed.