A motorboat provides for a regular transportation of passengers from point P to point Q and back again, both points being located on the same side of riverbank. If the actual speed of the boat (in still water) becomes twice of the original speed, then the trip from point P to Q and back again would take half time, which the boat usually spends on the way from P to Q and back again.
What is the ratio of the actual speed of the boat and the speed of the river flow?
a. sqrt(3):1
b. sqrt(5):1
c. sqrt(6):1
d. sqrt(2):1
e. None of these