This is the concept of rates we are required to get the time taken two drive between two points stated;
here we use the formula;
speed=distance/time
therefore;
distance=speed*time
the distance covered by the driver given that he drove for 4 hours at a speed of 40 mph;
thus;
distance=40*4=160 miles
thus the time taken if he traveled at a speed of 55 mph will be:
time=distance/speed
time=160/55
time=2.9090≈2.91 hours
The correct answer is A